Major cleanup, use Gradle properties and providers

[sciwhiz12]

This PR does a major cleanup of ForgeGradle tasks and plugins. The list of changes are too numerous to individually list out (you can read the commits to see all changes), so here are the two three key and most notable points:

• Apply the concepts found in the Lazy Configuration chapter of the Gradle User Guide. This includes the use of Property<T>, ConfigurableFileCollection, and co., providing two distinct advantages: allowing buildscript configuration of task and extension properties without needing to make more adjustments in afterEvaluate, and being able to avoid task creation unless necessary for execution.
• Refactors some classes to new packages, and splitting code. Notably, a number of methods in Util have moved to specialized subclasses such as DownloadUtil and EnvironmentChecks.
• Bumps minimum Gradle version to 7.1.

Buildscripts for user development (using the net.minecraftforge.gradle plugin) may need adjustments if they are manually adjusting tasks. Testing with a fresh MDK for 1.16.5 reveals no changes necessary (other than the required Gradle update and changing the ForgeGradle version).

Buildscripts for the Forge development workspace (the MinecraftForge repository) require more extensive changes. For reference, my fork's fg5 branch shows the changes needed for ForgeGradle 5 from this PR to run. To run the branch, clone this branch to an adjacent directory to the repository folder named ForgeGradle.

As of writing this description, this PR is marked as a draft due to insufficient testing (due to my insufficient hardware). ^{/cc @SizableShrimp pls test this PR as you promised me twice}

[LexManos]

Just a note, this is the major thing pending before a RB/No more breaking changes in FG5. We wanted to make sure we updated the modern gradle concepts to make the lifecycle of FG5/G7 consistent. So if people could test this and give feedback that'd be great.

[SizableShrimp]

Just a note, this is the major thing pending before a RB/No more breaking changes in FG5. We wanted to make sure we updated the modern gradle concepts to make the lifecycle of FG5/G7 consistent. So if people could test this and give feedback that'd be great.

Some preliminary testing shows it works with Forgedev for 1.17 and Userdev for both 1.16 and 1.17. Should be ready for review & merge. Since this is mostly just gradle updates to use more modern features, it shouldn't break or change much in terms of functionality. However, the more testing, the better. If anyone would like to test this still before it is merged and doesn't want to go through the trouble of cloning this locally, you can use my maven https://sizableshrimp.me/maven with a Group ID of me.sizableshrimp.gradlecleanup to test (FG5 only).