Stryker4s v0.15.1

This patch release mostly refactors some internal module layout.

For Maven users, the default files to mutate configuration now uses Maven project info. For sbt users, using a snapshot release of the plugin will no longer require also adding a snapshot resolver to your project too (it is done automatically now).

🐛 Bugfixes

• Add snapshot resolver if snapshot version is used in sbt plugin (#1457) @hugo-vrijswijk
• Use Maven project info to resolve files to mutate (#1454) @hugo-vrijswijk

🧰 Maintenance

• Test CI on JDK 21 (#1456) @hugo-vrijswijk
• Move some packages and remove unused ext methods (#1455) @hugo-vrijswijk
• Add munit to testkit (#1453) @hugo-vrijswijk
• Add api and testkit projects (#1449) @hugo-vrijswijk
• modules structure (#1448) @hugo-vrijswijk
• Use cats option/either syntax (#1440) @hugo-vrijswijk