Added 1.21.1 mod targets

- Build Fabric, Forge and NeoForge per target listed in gradle/mod-targets.json (1.21.1, 26.3)
- Add 1.21.1 adapter source overlays under adapters/*/src/versions/1.21.1
- Add verifyModdedMatrix and per-target Java runtime verification of loader jars
- Re-inject persistent dimensions from the levels-ready hook before the watchdog starts
- Wait for queued chunks and the final save before pregen completes
- Add the 1.21.1 data version and datapack supported_formats range
- Cascade regions whose sea or shore pool loses every biome
- Use Gson calls available on the 1.21.1 runtime

gradle/modded-generation-build-revision.gradle

@@ -18,7 +18,8 @@ TaskProvider<JavaExec> resolvedRevisionVerification = tasks.register('verifyReso
     classpath = files('../../buildSrc/build/libs/buildSrc.jar')
     mainClass.set('art.arcane.iris.buildtools.GenerationBuildRevision')
     doFirst {
-        List<String> arguments = ['verify-dependencies', file('../../core/build/generated/generation-revision/META-INF/iris/generation-kernels/abi-1.revision').absolutePath]
+        String runtimeVariant = providers.gradleProperty('irisRuntimeJava').getOrElse(irisModTarget.java.toString()) == '21' ? 'java21/' : ''
+        List<String> arguments = ['verify-dependencies', file("../../core/build/${runtimeVariant}generated/generation-revision/META-INF/iris/generation-kernels/abi-1.revision").absolutePath]
         for (ResolvedArtifact artifact : configurations.bundle.resolvedConfiguration.resolvedArtifacts) {
             String group = artifact.moduleVersion.id.group
             String name = artifact.moduleVersion.id.name