resolution time has *quadrupled* between 235d77457 and 6fa61b810

[arielb1]

Before (on librustc):

time: 0.013; rss: 169MB language item collection
time: 0.281; rss: 201MB resolution

After (on same librustc):

time: 0.017; rss: 226MB language item collection
time: 1.055; rss: 277MB resolution

cc @jseyfried

[arielb1]

The extra RAM usage seems to be because of the AST not getting freed after the early lint checks. Not sure if this is intentional.

[jonas-schievink]

The AST should definitely still get freed, nobody touched the code doing that, so it's not intentional (unless something about the command line options has changed?)

[jseyfried]

The performance regression in resolve looks like it was caused by #32328. I'll work on a fix now.
I'm not sure what caused the RAM increase.

[retep998]

Resolution used to take about 1 seconds a few months ago in winapi and now it takes 9 seconds.

[jseyfried]

I fixed the performance regression in #33064.