[clang] [clang-cl] Map /Ot to -O3 instead of -O2 (PR #95406)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

If we're trying to match MSVC, the amount of inlining MSVC does at /O2 is probably closer to what clang does at -O2 than -O3.  Which is why it was mapped that way in 015ce0f68f791b3abec4225c1b2e532ce5020174, I think.  clang's -O3 is really aggressive (which tends to look good in benchmarks, but less so in real software).

I'm a bit worried we're going to get a wave of complaints about codesize in reaction to this.

https://github.com/llvm/llvm-project/pull/95406