Fix argon volume-aware hitsounds not correctly playing immediately after object placement

[bdach]

Closes #29832.

The underlying reason for the incorrect sample playback was an equality comparer failure.

Samples are contained in several pools which are managed by the playfield. In particular, the pools are keyed by ISampleInfo instances:

osu/osu.Game/Rulesets/UI/Playfield.cs

Lines 457 to 464 in ccf1acc

	private DrawablePool<PoolableSkinnableSample> prepareSamplePool(ISampleInfo sampleInfo)
	{
	if (samplePools.TryGetValue(sampleInfo, out var pool)) return pool;
	AddInternal(samplePools[sampleInfo] = pool = new DrawableSamplePool(sampleInfo, 1));
	return pool;
	}

This means that for correct operation, ISampleInfo has to implement IEquatable<ISampleInfo> and also provide an appropriately correct GetHashCode() implementation. Different audible samples must not compare equal to each other when represented by ISampleInfo.

As it turns out, VolumeAwareHitSampleInfo failed on this, due to not overriding equality members. Therefore, a new HitSampleInfo(HitSampleInfo.HIT_NORMAL, HitSampleInfo.BANK_NORMAL, volume: 70) was allowed to compare equal to a VolumeAwareHitSampleInfo wrapping it, even though they correspond to completely different sounds and go through entirely different lookup path sequences.

Therefore, to fix, provide more proper equality implementations for VolumeAwareHitSampleInfo.

When testing note that this issue only occurs immediately after placing an object. Saving and re-entering editor makes this issue go away. I haven't looked too long into why, but the general gist of it is ordering; it appears that a normal-hitnormal pool exists at point of query of a new object placement, but does not seem to exist when entering editor afresh. That said I'm not sure that ordering aspect of this bug matters much if at all, since the two IHitSampleInfos should never be allowed to alias with each other at all wrt equality.