Limit size of search query for postgresql search

What does this MR do?

This MR implements limits for the search#show action: maximum of 64 terms or 4096 characters for non ES searches to prevent stack level too deep error from #31074 (closed).

If params[:search] is too big, it renders a flash[:alert] and prevents search from happening.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.