Now that most of the type-checker is using the object-coloring mechanism
to detect cycles, remove the explicit path parameter from the functions
that don't rely on it anymore.

Some of the syntactic-based resolver code (for aliases, interfaces)
still use an explicit path; leaving those unchanged for now.

The function cycle was moved from typexpr.go (where it is not used
anymore) to resolver.go (where it's still used). It has not changed.

Fixes #25773.

Change-Id: I2100adc8d66d5da9de9277dee94a1f08e5a88487
Reviewed-on: https://go-review.googlesource.com/130476Reviewed-by: Alan Donovan <adonovan@google.com>