Improved performance and reduced memory usage

[liabru]

This PR focuses on performance improvements around memory usage.

Scenes with a large number of colliding pairs will benefit most from these changes.

On the stress3, stress4 examples using the benchmark command in Node running on my Mac M1 Air:

• improved average performance up to ~6%
• reduced average memory usage up to ~30%
• reduced minor and major memory GC frequency / duration
• smoother frame rates as a result

Other examples show smaller improvements as they tend to have a much lower number of colliding pairs.

Changes

• optimised Pairs.update
• reduced array resizing and object disposal
• increased object reuse and caching
• increased local variable caching
• changed to a more compact Pair.id format
• changes to collision.supports as below

Migration

• Matter.Collision use collision.supportCount instead of collision.supports.length for active supports
• Matter.Pair use pair.contacts instead of pair.activeContacts
• Matter.Pair use pair.contactCount instead of pair.contacts.length for active contacts
• Pair.id format has changed

[photonstorm]

Just to say that I merged this PR into the version of Matter I use with Phaser and it worked great in all of my tests except one: When sleeping is enabled, collisions between sleeping bodies get removed from the Pairs list too early and things start to fall through each other / the world. I noticed there was a fix for this in #1079 but it wasn't included in this PR so I think gets lost?

[liabru]

@photonstorm thanks for taking a look - I've pushed an update re. sleeping bodies here, hopefully that covers it?

[liabru]

@photonstorm I've just pushed a couple more changes to handle pair removal in composite removal cases, that might be the last part here so I think I'll get this merged soon but feel free to let me know if you spotted anything else on this.

[MaxBittker]

woot