Add word break style to branch name in dropdown

What does this MR do?

Accounts for better user experience when there is a long branch name within the select a branch name dropdown. Long branch name will now appear on multiple lines, supporting word break.

❌ Issue

✅Result

Affected Areas

1. Create a new branch with an extremely long name

• Example: mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm

2. Ensure all these pages' branch dropdown shows the entirety of the extremely long branch name and appears broken up.

• Project > Details page
• Repository > Files page
• Repository > Commits page
• Repository > Contributors page

Tested on:

• IE11, Edge, Safari, Chrome, Firefox

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #62154 (closed)