cmd/compile: constraint satisfaction errors use "implements" instead of "satisfies"

[griesemer]

Per the latest spec, we now distinguish between interface implementation and constraint satisfaction.

However, currently the compiler reports constraint satisfaction errors with the phrase "cannot implement" or "does not implement" instead of "cannot satisfy" or "does not satisfy".

Not necessarily a release blocker but would be good to fix ASAP.

[griesemer]

cc: @findleyr

[gopherbot]

Change https://go.dev/cl/460396 mentions this issue: cmd/compile: use "satisfies" (not "implements") for constraint errors

[griesemer]

cc: @golang/release to decide if the CL above is acceptable to submit for 1.20. The change only affects error messages, but of those it affects virtually every error message about constraint satisfaction. It would be good to use the same language in those messages as is now used in the spec.

[heschi]

Fine by us; seems like a straightforward bug fix even if it's not so critical.