[llvm-profgen] On-demand track optimized-away inlinees for preinliner.

Tracking optimized-away inlinees based on all probes in a binary is expansive in terms of memory usage I'm making the tracking on-demand based on profiled functions only. This saves about 10%  memory overall for a medium-sized benchmark.

Before:

   note: After parsePerfTraces
   note: Thu Jan 27 18:42:09 2022
   note: VM: 8.68 GB   RSS: 8.39 GB
   note: After computeSizeForProfiledFunctions
   note: Thu Jan 27 18:42:41 2022
   note: **VM: 10.63 GB   RSS: 10.20 GB**
   note: After generateProbeBasedProfile
   note: Thu Jan 27 18:45:49 2022
   note: VM: 25.00 GB   RSS: 24.95 GB
   note: After postProcessProfiles
   note: Thu Jan 27 18:49:29 2022
   note: VM: 26.34 GB   RSS: 26.27 GB

After:
   note: After parsePerfTraces
   note: Fri Jan 28 12:04:49 2022
   note: VM: 8.68 GB   RSS: 7.65 GB
   note: After computeSizeForProfiledFunctions
   note: Fri Jan 28 12:05:26 2022
   note: **VM: 8.68 GB   RSS: 8.42 GB**
   note: After generateProbeBasedProfile
   note: Fri Jan 28 12:08:03 2022
   note: VM: 22.93 GB   RSS: 22.89 GB
   note: After postProcessProfiles
   note: Fri Jan 28 12:11:30 2022
   note: VM: 24.27 GB   RSS: 24.22 GB

This should be a no-diff change in terms of profile quality.

Reviewed By: wenlei

Differential Revision: https://reviews.llvm.org/D118515