Allow adding commits to a release

### Problem Statement

The [`OrganizationReleaseDetails`](https://github.com/getsentry/sentry/blob/efd3bdf63c642a9ac56e097db5929c806b013d9c/src/sentry/api/endpoints/organization_release_details.py#L294) and [`ProjectReleaseDetailsEndpoint`](https://github.com/getsentry/sentry/blob/efd3bdf63c642a9ac56e097db5929c806b013d9c/src/sentry/api/endpoints/project_release_details.py#L23) endpoint's PUT method lack support for adding commits to the release. Instead, when provided with a list of commits, these endpoints overwrite all of the commits already existing on the release.

Most likely, we will want to keep the current behavior, with commits overriding existing commits. However, we should also add the ability to add commits (via another parameter, another endpoint, etc).

### Solution Brainstorm

Most likely, we will want to keep the current behavior, with commits passed to the PUT request overwriting the existing commits. That way, we ensure backwards-compatibility with any API users who expect the API to work this way.

However, we should also add the ability to add commits (via another parameter, another endpoint, etc).

Adding this feature will unblock https://github.com/getsentry/sentry-cli/issues/2499 because we cannot currently add additional commits to an existing release without overwriting the commits that were there before.

### Product Area

Releases

Start by reading the PUT methods in src/sentry/api/endpoints/organization_release_details.py and src/sentry/api/endpoints/project_release_details.py. Trace how the current commits parameter replaces existing commits, then determine an additive API behavior while preserving that compatibility. Done means clients can add commits to an existing release without overwriting its current commits.

Written by the indexing model from the issue text.