[dev.typeparams] cmd/compile: allow go'd closure to escape when compiling runtime

When compiling runtime, we don't allow closures to escape,
because we don't want (implicit) allocations to occur when it is
not okay to allocate (e.g. in the allocator itself). However, for
go statement, it already allocates a new goroutine anyway. It is
okay to allocate the closure. Allow it.

Also include the closure's name when reporting error.

Updates #40724.

Change-Id: Id7574ed17cc27709609a059c4eaa67ba1c4436dc
Reviewed-on: https://go-review.googlesource.com/c/go/+/325109


Trust: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>