[clang-tools-extra] [clang-tidy] Add `bugprone-pointer-arithmetic-on-polymorphic-object` check (PR #91951)

[via cfe-commits]

https://github.com/Discookie commented:

I found a curious report when browsing through the results for `llvm-project`: [MemoryBuffer.cpp](https://codechecker-demo.eastus.cloudapp.azure.com/Default/report-detail?review-status=Unreviewed&review-status=Confirmed%20bug&detection-status=New&detection-status=Reopened&detection-status=Unresolved&run=llvm-project_llvmorg-12.0.0_ctr56-allow-inherited&report-id=5498248&report-hash=2e0e0ee19429584af2a682c9efb1cdf4&report-filepath=%2Flocal%2Fpersistent_docker%2FCSA-measurements-driver-2931%2Fmeasurements_workspace%2Fllvm-project%2Fllvm%2Flib%2FSupport%2FMemoryBuffer.cpp)
I have no idea where these spurious fixits could be coming from. My check doesn't emit any. Could this be because of the source range I'm piping into my diagnostic, or is it just some side-effect of other checks, or maybe the Tidy module? I'll investigate and fix this before merging.

Other than this case, fixed the reviews. I'm debating adding a flag for virtual destructor only as well, but I haven't seen a case in the wild where it was the only inherited function.

Made IgnoreInheritedVirtualFunctions `false` by default - doesn't have too many meaningful differences, but it does have more reports. [Results on projects](https://codechecker-demo.eastus.cloudapp.azure.com/Default/runs?run=ctr56%2ainherited)

https://github.com/llvm/llvm-project/pull/91951