Replicate vanilla's loading progess bar better

[Jab125]

Better replicate the vanilla progress bar copying over the logic from LoadingOverlay

I've copied the functionality of LoadingOverlay#currentProgress (which is used to render vanilla's progress bar) to the NeoForge overlay.

Minecraft uses this.currentProgress = Mth.clamp(this.currentProgress * 0.95F + f6 * 0.050000012F, 0.0F, 1.0F); where f6 is this.reload.getActualProgress(). Right now, NeoForge only uses this.reload.getActualProgress().

(Visible changes are a smooth progress bar and the very end of the progress bar being slower.)

This PR uses the copied over currentProgress field instead of just this.reload.getActualProgress():

+ this.currentProgress = Mth.clamp(this.currentProgress * 0.95F + this.reload.getActualProgress() * 0.05F, 0.0F, 1.0F);
+ progressMeter.setAbsolute(Mth.ceil(this.currentProgress * 1000));
- progress.setAbsolute(Mth.clamp((int) (this.reload.getActualProgress() * 100f), 0, 100));

It also moves the progressMeter.complete(); call to when the overlay is closed as well as increasing the progress bar's steps to 1000 for 10x smoothness.

One place where the progress bar is different is that vanilla fades the progress bar out when it is done. This can't be done in this PR due to needing to add support in FancyModLoader.