[MC] Move MCTargetOptions pointer from MCContext to MCAsmInfo (#180464)
Except MC-internal `MCAsmInfo()` uses, MCAsmInfo is always constructed
with `const MCTargetOptions &` via `TargetRegistry::createMCAsmInfo`
(https://reviews.llvm.org/D41349). Store the pointer in MCAsmInfo and
change `MCContext::getTargetOptions()` to retrieve it from there,
removing the `MCTargetOptions const *TargetOptions` member from
MCContext.
MCContext's constructor still accepts an MCTargetOptions parameter
for now but is often omitted by call sites.
A subsequent change will remove this parameter and update all callers.