internal/bytealg: use CBZ instructions
internal/bytealg: use CBZ instructions

Use CBZ to replace the comparison and jump to the zero instruction in the arm64 assembly file.

Change-Id: Ie16fb52e27b4d327343e119ebc0f0ca756437bc4
Reviewed-on: https://go-review.googlesource.com/c/go/+/237477
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>
Run-TryBot: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

cloudflare/go,CAFxX/go,CAFxX/go,golang/go,CAFxX/go,golang/go,golang/go,cloudflare/go,golang/go,CAFxX/go,golang/go,cloudflare/go,cloudflare/go,cloudflare/go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,nawawi/go,golang/go,cloudflare/go,nawawi/go,nawawi/go,nawawi/go,nawawi/go,golang/go,cloudflare/go,nawawi/go,CAFxX/go