Transform decompile step into a task that is customizable via specific settings

[shartte]

TODO

• Convention the properties to Gradle properties so they're easy to set via gradle.properties (e.g. neogradle.subsystems.decompiler.maxMemory=4g)

Example:

subsystems {
  decompiler {
    maxMemory = "2g"
    maxThreads = 4
    logLevel = DecompilerLogLevel.TRACE
    jvmArgs = ["-verbose:gc']
  }
}

[shartte]

@marchermans Added the property binding and at least added some docs to README.md about them, otherwise we'll surely forget to ever document them 😓

[Matyrobbrt]

This should link to https://projects.neoforged.net/neoforged/neogradle as it provides copy buttons.