[clang] Thread safety analysis: Allocate FactEntrys with BumpPtrAllocator (PR #149660)

[Aaron Puchert via cfe-commits]

aaronpuchert wrote:

> Overall compilation before the change takes 327,801,317 instructions, and 327,433,878 after the change

Accidentally left assertions on. Without it's 277,111,134 versus 276,855,186, but this is also 0.1%, and Thread Safety Analysis is still roughly 1% of the overall compilation time.

https://github.com/llvm/llvm-project/pull/149660