Build/Test Tools: Trim down the upgrade testing matrix.

The upgrade testing workflow is currently at ~978 jobs spawned from the strategy matrix. While it's great to test all possible combinations, GitHub's UI cannot keep up with tracking that number of jobs, often taking 30-45 minutes to accurately report the outcome even though the jobs themselves all complete in under 5 minutes.

This is 2x the total number of concurrent jobs allowed for the entire organization (which creates a backlog and slows everything down even more).

This trims down the number of combinations included in the testing matrices to be a bit more thoughtful following the following methodology:

- The last two releases of WordPress are tested against all PHP and MySQL LTS version combinations and the most recent innovation release.
- The next 6 oldest versions of WordPress are tested against both the oldest and newest releases of PHP currently supported for both PHP 7 & 8 along with the oldest and newest MySQL LTS versions currently supported (no innovation releases).
- For the remaining versions of WordPress receiving security updates, they are only included if the database version was different that the previous major release.
- The oldest version of WordPress receiving security updates should always be tested against the same full list of combinations as the last two releases.

When choosing which MySQL versions to test against:

- Only the most recent innovation release should be included in testing.
- Even though MySQL >= 5.5.5 is currently supported, there are no 5.5.x Docker containers available that work on modern architectures.
- 5.6.x Docker containers are available and work, but 5.6 only accounts for ~2.3% of installs as of 12/6/2024.defaults:
- 5.7.x accounts for ~20% of installs, so this is used below instead.

With these changes, the total number of jobs is reduced by ~58%.

Props johnbillion, mukesh27.
See #62221.
Built from https://develop.svn.wordpress.org/trunk@59508


git-svn-id: http://core.svn.wordpress.org/trunk@58894 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.8-alpha-59507';
+$wp_version = '6.8-alpha-59508';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.