runtime: break out the debug.malloc codepaths into functions
This change breaks out the debug.malloc codepaths into dedicated
functions, both for making mallocgc easier to read, and to reduce the
function's size (currently all that code is inlined and really doesn't
need to be).
This is a microoptimization that on its own changes very little, but
together with other optimizations and a breaking up of the various
malloc paths will matter all together ("death by a thousand cuts").
Change-Id: I30b3ab4a1f349ba85b4a1b5b2c399abcdfe4844f
Reviewed-on: https://go-review.googlesource.com/c/go/+/617879 Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>