[llvm] [TTI] Constify BasicTTIImplBase::thisT() (PR #136567)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

Yeah, not so easy as it looked :laughing: 
```
Total Discovered Tests: 65267
  Skipped          :    16 (0.02%)
  Unsupported      :   328 (0.50%)
  Passed           : 64432 (98.72%)
  Expectedly Failed:   186 (0.28%)
  Failed           :   305 (0.47%)
```
Apparently, fixing compilation errors is not enough.


https://github.com/llvm/llvm-project/pull/136567