internal/buildcfg: enabled CoverageRedesign GOEXPERIMENT by default
internal/buildcfg: enabled CoverageRedesign GOEXPERIMENT by default

Turn on the CoverageRedesign GOEXPERIMENT by default.

Updates #51430.

Change-Id: Id15c67ef0b6ac421b188d163fd2ce4a302abb3c9
Reviewed-on: https://go-review.googlesource.com/c/go/+/436236
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Run-TryBot: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go