[xla_compile][NFC] Allow loading autotune results from a SymbolRepository.
[xla_compile][NFC] Allow loading autotune results from a SymbolRepository.

Doing so allows recompilation of uploaded modules with autotune results to
mimic more cases...and allows full recompilation without GPU hardware.

We now have enough arguments in XlaCompileMain that it's time to extract some
options structs, which significantly improved usability at the cost of verbose
code in places.
