Game Test API crashing regular runs with seperated source sets.

[JustPyrrha]

When separating gametest code into its own source set, as the javadocs suggest, the testing library still trys to load the gametest entrypoint during regular runs causing a crash.

Expected Behaviour

The testing library only attempts to load quilt:game_test entrypoints when the quilt.game_test property is set to true.

Actual Behaviour

The testing library always trys to load quilt:game_test entrypoints during its own init entrypoint without checking if its a testing run.

Replication Steps

1. Clone https://github.com/JustPyrrha/qsl-testing-bug (minimal replication project)
2. Run either of the standard client or server runs.

Tested in both dev and prod environments. Dev using the above project with only qsl_base and testing (6.1.2+1.20.1), and prod using the above project and the latest qsl from modrinth (7.4.0+0.90.0-1.20.1).

[LambdAurora]

You're supposed to create a new QMJ file in the separate source set as if it was a new mod (like it is done in QSL).

[JustPyrrha]

ah that makes more sense, though the separate qmj isn't mentioned in the javadocs so that might be worth updating.

 * <p>
 * <h3>Get Started</h3>
 * Writing tests for your mod is relatively simple: create a new class that extends {@link org.quiltmc.qsl.testing.api.game.QuiltGameTest}, and add it
 * as an entrypoint of key {@value org.quiltmc.qsl.testing.api.game.QuiltGameTest#ENTRYPOINT_KEY}.
 * <p>