Closes https://github.com/zed-industries/zed/issues/57053

Decided to be on a safest side and made only the code lens' blocks to
hide in folds: let me know if that's not desired and we should hide all
blocks (e.g. ctrl-enter for inline assist block is also not hiding and
looks odd).

Ran `ITERATIONS=100000 OPERATIONS=10 cargo test --profile release-fast
-p editor --lib display_map::tests::test_random_display_map --
--nocapture` and it passes successfully.

`SEED=770 OPERATIONS=50 cargo test --profile release-fast -p editor
--lib display_map::tests::test_random_display_map` seems to fail even on
`main`

Before:

<img width="392" height="155" alt="before"
src="https://github.com/user-attachments/assets/44d1a500-7512-49de-a9bd-2837c33353a9"
/>

After:

<img width="338" height="159" alt="after"
src="https://github.com/user-attachments/assets/671791d8-a443-4ca2-abb2-8049fe8910a7"
/>


Release Notes:

- Fixed code lens not hiding for folded regions