Update Gradle wrapper and Fabric Loom

[Steveplays28]

• Updated Gradle wrapper to v8.11.1
• Updated Fabric Loom to v1.9.2

Also moved the Fabric Loom version declaration into gradle.properties, using settings.gradle.
I also removed java.toolchain.languageVersion = JavaLanguageVersion.of(21), that should be redundant with:

    tasks.withType<JavaCompile> {
        options.encoding = "UTF-8"
        options.release.set(21)
    }

which is already present in the subprojects block of build.gradle.kts.