Filter by name when protecting branch in E2E test

What does this MR do and why?

Resolves #386769 (closed) specifically #386769 (comment 1223723365)

With this MR, the E2E test fills in the name of the user (or group) first before clicking the user (or group). This should avoid the test failing when there is too many users (or groups) in the environment.

How to set up and validate locally

• bundle exec rspec qa/specs/features/ee/browser_ui/3_create/repository/restrict_push_protected_branch_spec.rb
• bundle exec rspec qa/specs/features/ee/browser_ui/3_create/repository/assign_code_owners_spec.rb

(These are the only tests that use the Resource::ProtectedBranch.fabricate_via_browser_ui! method)

MR acceptance checklist

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