feat: use signed-urls for email confirmation

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 32.53012% with 56 lines in your changes missing coverage. Please review.

:white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/sentry/users/web/accounts.py	23.63%	42 Missing :warning:
src/sentry/users/api/endpoints/user_emails.py	57.14%	8 Missing and 1 partial :warning:
src/sentry/users/models/user.py	16.66%	5 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #81044 +/- ## ========================================== - Coverage 78.48% 78.46% -0.02% ========================================== Files 7210 7211 +1 Lines 319517 319622 +105 Branches 43983 43992 +9 ========================================== + Hits 250758 250800 +42 - Misses 62358 62418 +60 - Partials 6401 6404 +3 ```