Renames the existing pw::sync::SpinLock to InterruptSpinLock to
make it obvious that this is not just a spin lock and that interrupt
masking is included.
This change leaves C++ & GN redirects in place in order to support
migrating Pigweed and customers in follow up changes.
Change-Id: If9fb5594e7d71778b15cd15a9cd7ec71ca0e403b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/37560
Commit-Queue: Ewout van Bekkum <ewout@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>