Makes it so that strategies project env strategies that aren't draggable
don't get the drag icon. The reason it didn't work as expected was that
we used fallback functions instead of keeping them undefined.
I discovered that we applied two dragging boxes, so I removed the outer
layer one (specific to project envs) in favor of relying on the inner
one. Most of the lines changed are just indentation as a result of this
nesting going away.
Here's the diff. The top set of strategies aren't draggable; the lower
ones are.

Gives a small update in how we deal with unevaluated and disabled
strategies in the new playground design:
- "Unevaluated" badges go from yellow warning to blue info and their
text changed to "Not evaluated"
- Don't show "Not evaluated" badges on strategies that are disabled.
To avoid this change affecting the current playground setup, I
duplicated the old resultschip into a legacy file and changed the
existing impl. To avoid updating all other files that use that chip
(it's all over the playground) and checking flags or creating duplicates
there, I decided to do a quick check at the top of the legacy file and
use the new file if the flag is on.
In doing so, I've also simplified the actual chip file and have more or
less cut the total line count in it in two 😄

Flattens the list of strategies when you have both release plans and
strategies. If you had both, you'd have this setup before:
```
- ol
- li // release plan
- ol // release plan strategies
- li // regular strategies
- ol // strategy list
```
Now we drop the extra nesting:
```
- ol
- li // release plan
- ol // release plan strategies
- li // the rest of the strategies
```
Semantically, I think this is just as valid and it simplifies a lot of
styling that no longer needs to look for other lists etc.
As part of doing this, I have also moved the "many strategies" warnings
and pagination labels to outside the list instead of inside the smaller
list.
Otherwise, the list looks just the same as before and drag-n-drop works
just fine.
(side note: these strategies shouldn't have drag handles 🤔 )

As a bonus, this PR also:
- Uses the disabled style separator for disabled strats in playground
and deletes some unused components I found.
Playground disabled strats (we probably don't want double orange badges;
I'll talk to UX):

Handle cases where flags have no strategies in the playground.
As part of this, also changes how we deal with the padding/margins in
the playground: instead of making all but one items in the playground
have to explicitly add padding, now we instead say that the only item
that needs to do something is the list, which uses negative inline
margins.
This also has the added benefit of adding all the top-level elements
(that is: that's not part of the strategy lists) inside the same
container, so we can control gaps between them with flex's gaps.
When you have no strategies (before):

When you have no strategies (after):

Implements playground results for strategies.
Old design:

New design:

Still left: segments.
I also discovered during this that some of the new hooks (and also some
of the new components) accept deprecated types
(`IFeatureStrategyPayload` in this case). If that should indeed be
deprecated, then we also shouldn't use it in the new hooks / components
if we can avoid it. I'll make a task for it.
---------
Co-authored-by: Tymoteusz Czech <2625371+Tymek@users.noreply.github.com>
Implements the new design for playground constraints. They're not in use
in segments yet, and strategy parameters have not been touched. This PR
establishes a pattern that we can follow for strategies and parameters
later.

The PR also includes a change in how the constraint item organizes its
children: it now takes care adding padding and spacing itself, instead
of the children doing that. It looks right most places, but segments
aren't quite right anymore. However, as this is behind a flag, I'd
rather fix that in a separate PR.
---------
Co-authored-by: Tymoteusz Czech <2625371+Tymek@users.noreply.github.com>
Previously, the entire card was draggable, which meant that you couldn't
select text inside the card or inside the milestone title when editing.
This makes it so that only the drag handle is draggable.
Fixes a number of issues that would surface in UTC-n (where n > 1)
timezones. I've not found a way to check this with tests (and it looks
like [we weren't able to last time
either](https://github.com/Unleash/unleash/pull/9110/files#r1919746328)),
so all the testing's been done manually by adjusting my system time and
zone. (From what I understand, you can't generate a Date with a specific
TZ offset in JS: it's only utc or local time)
Resolved:
- [x] Selecting "Jan" in the dropdown results in the selection being
"December" (off by one in the selector)
- [x] Selecting a month view only gives you one data point (and it's
probably empty). Wrong date parsing on the way out resulted in sending
`{ from: "2025-02-28", to: "2025-02-28"}` instead of `{ from:
"2025-03-01", to: "2025-03-31"}`
- [x] The dates we create when making "daysRec" need to be adjusted.
They showed the wrong month, so the dates were off.
- [x] Make sure the labels are correct when hovering over. Again: we
used the wrong month for generating these.
- [x] The available months are wrong. Incorrect month parsing again.
- [x] The request summary month is wrong. You guessed it: incorrect
month parsing
- new way of showing strategy variants
- fixed wrapping issue in strategy editing, for a lot of variants
defined (`SplitPreviewSlider.tsx` change)
- aligned difference between API and manually added types
Initial rough work on adapting the playground strategies to the new
designs. This PR primarily splits components into Legacy files and adds
new replacements. There are *some* updates (including spacing and text
color), but nothing juicy yet. However, I wanted to get this in now,
before this PR grows even bigger.