Optimize strict generic signature checking performance

[ahejlsberg]

This PR optimizes the performance of strict generic signature checking introduced in #16368. When a generic class or interface is instantiated, each generic method in the class or interface is instantiated with a fresh set of cloned type parameters (which we need to handle scenarios where different generations of the same type parameter are in scope). This leads to a lot of new type identities, and potentially a lot of work comparing those identities in strict generic checking mode. As an optimization we now base signature comparisons on "canonical instantiations" that uses a single type identity for all unconstrained type parameters.

Projects that make heavy use of generic methods see dramatically improved type check times. For example:

• https://github.com/falsandtru/spica: From 4.24s to 1.83s.
• https://github.com/arturkulig/immview: From 18.25s to 1.35s.
• https://github.com/emmanueltouzery/prelude.ts: From 21.34s to 0.93s.

Only changes in RWC baselines are missing error elaborations due to improved sharing.

Fixes #18257.

[sandersn]

Looks good!

[DanielRosenwasser]

@falsandtru @arturkulig @emmanueltouzery you may want to take a look at our nightlies once this gets merged in!

[arturkulig]

sorry taking so long.

It works! 🎉

with immview everything was ok even without that fix, but just changing types to extended interfaces, but I have other, commercial private project in TS and I run into the same issue where type checking whole project was impossible anymore and the same trick as with immview did not work. So as you suggested today I installed latest version from npm (2.6.0-dev-something) and it completes!
I no longer have compile it with increasing --max-old-space-size on node to run type checking too, but I'm going to leave this note here for people that would like to know cheap and very unreliable workaround for 2.5