chore: rename `RepoIcon` to `CodeHostIcon`

Created by: limitedmage

Part of #34237 (closed)

The name RepoIcon is confusing (it could refer to either of the two icons shown next to the repo in search results). Renaming to clarify that this is the icon of the code host (GitHub, GitLab, etc).

Test plan

Rename change only, CI checks should be enough.

App preview:

• Web
• Storybook

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