Remove usage of finalizers wherever possible

[peppy]

While investigating ppy/osu#11800, we have basically identified the root cause to be the presence of objects with finalizers (even if they have been suppressed) existing in the finalizer queue.

Using the following model classes:

public class NonFinalizingThing
{
    public NonFinalizingThing()
    {
    }
}

public class FinalizingThing
{
    public FinalizingThing()
    {
    }

    ~FinalizingThing()
    {
    }
}

Constant allocations without finalizer:

for (int i = 0; i < 100000000; i++)
{
    var thing = new NonFinalizingThing();
}

With:

for (int i = 0; i < 100000000; i++)
{
    var thing = new FinalizingThing();
    GC.SuppressFinalize(thing);
}

Note the pause time increasing from 0.1ms to around 7ms.

[peppy]

Remaining classes which look to require the finalizer:

• VideoDecoder
• BassCallback (arguable, may want to make internal and avoid it, depending on alloc rate)
• FrameBuffer (GL resources)
• RenderBuffer (GL resources)
• VertexBuffer (GL resources)
• Icon (Native resources)
• TimePeriod (Native resources)
• BackgroundStackTraceCollector (thread cleanup; can probably be internalised / avoided but low impact)

Remaining classes to check / remove if possible, in order of impact:

• AudioComponent (high impact, needs checking)
• TextureGL (GL resources; can likely be moved to TextureGLSingle) (Move TextureGL's finalizer local to TextureGLSingle #4256)
• TextureWithRefCount (i believe we rely on it here, but maybe could be internalised)
• AsyncBufferStream (Remove finaliser from AsyncBufferStream #4306)

[peppy]

Unassigning self in case anyone wants to attempt the remaining ones.

[peppy]

I don't see any immediate way around the finalizer in TextureWithRefCount so I've marked that as complete. It's relatively low usage, at least (on a texture object which itself has pretty high memory/alloc overhead).