ref(transactions): dont send transactions to post_process

[JoshFerge]

Once we've deployed https://github.com/getsentry/sentry/pull/81079, we no longer need to send transactions to post_process.

We delete the redis key from the processing store right in save event as its no longer needed, and take advantage of the existing raw / skip_consume functionality to tell the event stream not to carry on the transaction to post_process after it's been inserted into snuba. https://github.com/getsentry/sentry/blob/dce58ed72c715cd5e44e0f2a71d48e598fbfeead/src/sentry/event_manager.py#L1144

Once this is merged and the option is turned on, we can delete all of the option code, as well as code that is no longer active in post_process.

part of https://github.com/getsentry/sentry/issues/81065

note that when this is deployed, there could be some transactions that go through post_process that do not have values in the processing store. this shouldn't cause problems, and wil monitor logs from post_process here: https://github.com/getsentry/sentry/blob/dce58ed72c715cd5e44e0f2a71d48e598fbfeead/src/sentry/tasks/post_process.py#L531

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line 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/tasks/store.py	75.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## jferg/tx-post-process-1 #81085 +/- ## ============================================================ + Coverage 57.52% 78.48% +20.95% ============================================================ Files 7204 7215 +11 Lines 319305 319819 +514 Branches 43991 44047 +56 ============================================================ + Hits 183686 251003 +67317 + Misses 130864 62421 -68443 - Partials 4755 6395 +1640 ```

[JoshFerge]

rollout strategy: https://github.com/getsentry/sentry/issues/81065#issuecomment-2491767459