Override all methods on value-types

[mgravell]

First, try and write a test that uses reflection to discover all struct (including non-public), and check whether all of Equals, GetHashCode and ToString are overridden

Next: do that! Feel free to use:

public override string ToString() => nameof(ThisType);
public override bool Equals(object? obj) => ThrowHelper.ThrowNotSupportedException<bool>();
public override int GetHashCode() => ThrowHelper.ThrowNotSupportedException<int>();

if there is no sane comparison; if there is a sane comparison (for example, PooledValueTaskSource could compare _source and _token), then it should also implement IEquatable<ThisType>, with (typical)

public override Equals(object? obj) => obj is ThisType other && Equals(other);
public bool Equals(ThisType other) {...}