Format asm! macro calls

[ytmimi]

Add support for formatting asm! macro calls.

Formatting for asm!is gated behind a new unstable foramt_asm_macro configuration value.

Tracking issue for the new configuration value can be found at #5210

The specific guidelines for formatting the macro are still being decided, but this PR goes a long way to formatting the various components of the asm! macro (templates, operands, clobber_abis, and options).