Student searchbar: Migrate to React component and optimize for larger lists

[kevinrobinson]

This builds on #2194 and replaces it.

Who is this PR for?

districtwide admin, school admin in large buildings

What problem does this PR fix?

This searchbar can be quite slow for districtwide admin or schoolwide admin in large buildings.

The existing jQuery autocomplete UI doesn't have good hooks for truncating the results returned, and uses a library we'd like to remove as a dependency to limit pieces of UI we depend on.

Right now the way the student searchbar matches it won't match last name, first name or with partial matches.

What does this PR do?

Updates the student searchbar so that it matches any part of the student name in any order (eg, either last name or first name first is fine). Replaces autocomplete with react-autocomplete, keeping the same sessionStorage caching.

Revise the label text ahead of potentially adding a new searchbar for the feed notes, and add a placeholder text to the input.

Add some optimizations for truncating large lists (eg, >500 students), and in that case offer to link to the My students page instead.

Screenshot (if adding a client-side feature)

This shows fake names from (fake_names.rb):

Checklists

Which features or pages does this PR touch?

• Core

Does this PR use tests to help verify we can deploy these changes quickly and confidently?

• Included specs for changes
• Improved specs for existing code in need of better test coverage
• Manual testing made more sense here

[kevinrobinson]

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