Automatically create release tags via GitHub actions

[tautschnig]

Release tags are now created automatically when including an indicator (see updated documentation) in the commit message.

For now: keep automated release tagging in dry-run mode (we should first make sure this actually works on this repository before enabling it in production).

This is a second attempt, see some prior discussion in #5649. This new attempt just reads the version to use for tagging off of config.inc rather than computing it from commit messages or the likes.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.38%. Comparing base (6752c40) to head (0dce756).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8424      +/-   ##
===========================================
+ Coverage    77.86%   78.38%   +0.52%     
===========================================
  Files         1726     1726              
  Lines       189890   188613    -1277     
  Branches     18221    18266      +45     
===========================================
  Hits        147849   147849              
+ Misses       42041    40764    -1277     

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[TGWDB]

If I understand correctly this will trigger on any changes to src/config.inc. Since we have more than only the version number here, my (late night/weekend) intuition is that we need to be more precise.