[lld, ELF and mac] Add --time-trace=<file>, remove --time-trace-file=<file>

`--time-trace=foo` has the same behavior as `--time-trace --time-trace-file=<file>`
had previously.

Also, for mac, make --time-trace-granularity *not* imply --time-trace, to match
behavior of the ELF port.

Differential Revision: https://reviews.llvm.org/D128451