Prepare 2.5.0rc1. (pantsbuild#12047)

* Prepare 2.5.0rc1

[ci skip-rust]
[ci skip-build-wheels]

src/python/pants/notes/2.5.x.md

@@ -2,6 +2,20 @@
 
 See https://www.pantsbuild.org/v2.5/docs/release-notes-2-5 for an overview of the changes in this release series.
 
+## 2.5.0rc1 (May 10, 2021)
+
+### New Features
+
+* Add `extra_env_vars` field to `python_tests` target (Cherry-pick of #12022) ([#12023](https://github.com/pantsbuild/pants/pull/12023))
+
+### Plugin API Changes
+
+* Auth plugins can inspect the prior result, set an expiration, and override `--remote-{store,execution}-address` (Cherry-pick of #12029) ([#12046](https://github.com/pantsbuild/pants/pull/12046))
+
+### Bug fixes
+
+* Fix `--remote-auth-plugin` and `--remote-oauth-bearer-token-path` to execute every run with Pantsd (#12020) ([#12031](https://github.com/pantsbuild/pants/pull/12031))
+
 ## 2.5.0rc0 (May 04, 2021)
 
 ### New Features