Enable RSA keygen becnhmarks by default (#2206)

### Description of changes: 
The current filter logic in the speed tool is a bit weird. It's not
possible to run all the benchmarks because RSA key gen was off by
default. If you pass in the filter "RSAKeyGen" you get the keygen
benchmarks and all the other RSA benchmarks. This change updates it to
be treated the same as all the other benchmarks.

The RSA key gen benchmarks are still a little weird because they
override the timeout which is why they are slower and take more time.
For now the canary use case is fine.

### Testing:
The CI will run this benchmark with all the libcryptos we expect to
support.

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license and the ISC license.

tool/speed.cc

@@ -417,8 +417,7 @@ static bool SpeedRSA(const std::string &selected) {
 }
 
 static bool SpeedRSAKeyGen(bool is_fips, const std::string &selected) {
-  // Don't run this by default because it's so slow.
-  if (selected != "RSAKeyGen") {
+  if (!selected.empty() && selected.find("RSAKeyGen") == std::string::npos) {
     return true;
   }