Fixes #39511 - Replace enzyme test in SearchInput with RTL

[kfamilonidis]

The three tests now verify real user-visible behavior (value, class, Clear button presence, focus state) +1 the Clear button behaviour onClick event that it was not previously tested.

[Lukshio]

Summary

Clean, focused enzyme->RTL migration for SearchInput. The three tests now verify real user-visible behavior (value, class, Clear button presence, focus state) instead of a snapshot. No functional concerns.

Critical (must fix before merge)

• None

Suggestions (should fix)

• Commit message uses Fixes #39511: ... - the documented Foreman convention (and what's used on develop, e.g. Fixes #38653 - Fix settings show endpoint) is Fixes #XXXXX - description with a hyphen, not a colon. Please reformat.
• The Clear button is only checked for presence (toBeInTheDocument), not behavior. Since RTL makes it easy, consider adding an interaction test with userEvent.click to verify clearing actually works (the old snapshot never covered this either, so it would be a net improvement).

Nice to have (optional)

• @testing-library/jest-dom is imported per-file here; worth double-checking whether Foreman's global Jest setup already extends expect with jest-dom matchers, in which case this import is redundant.

Checklist gaps

• PR description is just the commit title repeated - a short note on what behavior the new tests cover would help reviewers.

[kfamilonidis]

@Lukshio I added a test to onClear event