crypto/rsa: add benchmarks for not and partially optimized keys

crypto/rsa: add benchmarks for not and partially optimized keys

Updates #59695

Change-Id: I7944195c805cd9da819cdf2bd49ecb2423ccd73b
Reviewed-on: https://go-review.googlesource.com/c/go/+/637178
Auto-Submit: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>