Rollup merge of #78702 - wesleywiser:self_profile_cgu_sizes, r=Mark-Simulacrum

Rollup merge of #78702 - wesleywiser:self_profile_cgu_sizes, r=Mark-Simulacrum

[self-profiling] Include the estimated size of each cgu in the profile

This is helpful when looking for CGUs where the size estimate isn't a
good indicator of compilation time.

I verified that moving the profiling timer call doesn't affect the
results.

Results:

<img width="297" alt="Screen Shot 2020-11-03 at 7 25 04 AM" src="https://user-images.githubusercontent.com/831192/97985503-5901d100-1da6-11eb-9f10-f3e399702952.png">

`measureme` doesn't have support for custom arg names yet so `arg0` is the CGU name and `arg1` is the estimated size.