[XLA] [NFC] Do not duplicate flags in tooling for attributes we already have attached to HloModuleConfig
[XLA] [NFC] Do not duplicate flags in tooling for attributes we already have attached to HloModuleConfig

For --xla_dump_to and others, we already have flags auto-generated from
xla.proto, let's just use those instead of creating a new set of flags for each
binary, and then passing attributes across structs.
