refactor!: Rename UsersService.Edit to Update, introduce UserUpdateRequest, and pass request by value

[ManavSharma142]

BREAKING CHANGE: UsersService.Edit is now Update and uses a new UserUpdateRequest body value.

Relates to: #3644.

Rename UsersService.Edit to Update for consistency with GitHub API naming.
Introduce a dedicated UserUpdateRequest type containing only fields accepted by the update endpoint, and pass it by value instead of a pointer.

[gmlewis]

@ManavSharma142 - I edited the description to add two important lines.
Also, in the description you should cc: @JamBalaya56562 and @jvm986.

Now, you need to run tests locally following the guidance in CONTRIBUTING.md, especially step 4, and push the changes to this PR while trying to avoid force pushing when possible.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.55%. Comparing base (4a79475) to head (d69b8f1).

Additional details and impacted files

@@ Coverage Diff @@## master #4433 +/- ##
=======================================
Coverage 97.55% 97.55% =======================================
Files 194 194 Lines 19892 19892 =======================================
Hits 19406 19406 Misses 268 268 Partials 218 218 

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[gmlewis]

Thank you, @ManavSharma142!
LGTM.
Awaiting second LGTM+Approval from any other contributor to this repo before merging.

cc: @stevehipwell - @alexandear - @Not-Dhananjay-Mishra

[Not-Dhananjay-Mishra]

LGTM