controllers/krate/owners: Convert remaining endpoints to async/await

[Turbo87]

These were the last two API endpoints that were still using synchronous database operations. With this PR the two endpoints are now using diesel-async queries as well, allowing us to start the cleanup process of removing all of the duplicate sync functions.

Here is what GitHub Copilot has to say about the PR: 😅

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This pull request includes several changes to the src/controllers/krate/owners.rs, src/models/crate_owner_invitation.rs, src/models/krate.rs, src/models/owner.rs, src/models/team.rs, and src/models/user.rs files to transition from synchronous to asynchronous database operations using diesel_async.

Key changes include:

Transition to Asynchronous Database Operations:

• src/controllers/krate/owners.rs: Replaced synchronous diesel::RunQueryDsl with diesel_async::RunQueryDsl and removed spawn_blocking in favor of direct async calls.
• src/models/crate_owner_invitation.rs: Updated the create method and related transaction logic to use async/await patterns.
• src/models/krate.rs: Modified owner_add and owner_remove methods to be asynchronous.
• src/models/owner.rs: Converted find_or_create_by_login to an async function.
• src/models/team.rs: Updated create_or_update and create_or_update_github_team methods to use async/await.
• src/models/user.rs: Made the owning method asynchronous.

[codecov]

Codecov Report

Attention: Patch coverage is 99.29078% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.40%. Comparing base (05e3976) to head (8cd0ec5).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/controllers/krate/owners.rs	98.80%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10049      +/-   ##
==========================================
- Coverage   89.45%   89.40%   -0.06%     
==========================================
  Files         295      295              
  Lines       31243    31255      +12     
==========================================
- Hits        27949    27943       -6     
- Misses       3294     3312      +18     

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