gh-127330: Update for OpenSSL 3.4 & document+improve the update process (GH-127331)

- Add `git describe` output to headers generated by `make_ssl_data.py`

  This info is more important than the date when the file was generated.
  It does mean that the tool now requires a Git checkout of OpenSSL,
  not for example a release tarball.

- Regenerate the older file to add the info.
  To the other older file, add a note about manual edits.

- Add notes on how to add a new OpenSSL version

- Add 3.4 error messages and multissl tests

.github/workflows/build.yml

@@ -250,7 +250,8 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-24.04]
-        openssl_ver: [3.0.15, 3.1.7, 3.2.3, 3.3.2]
+        openssl_ver: [3.0.15, 3.1.7, 3.2.3, 3.3.2, 3.4.0]
+        # See Tools/ssl/make_ssl_data.py for notes on adding a new version
     env:
       OPENSSL_VER: ${{ matrix.openssl_ver }}
       MULTISSL_DIR: ${{ github.workspace }}/multissl