compiler: allow setting compiler options on individual methods
Allow `Base.Experimental.@optlevel` and `@compiler_options` to be applied
to a single function definition, recording `optlevel`, `compile` and
`infer` on the Method (and in its CodeInfo) instead of the enclosing
module. Unset options inherit from the module. In a `@generated` function
the expansion can override the options for an individual instance by
splicing the corresponding meta expression into the returned body.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>