Previously, roachtest nightly tests were limited to run on regular VMs.
In order to check FIPS functionality, we need to run the tests on
FIPS-enabled VMs.

This PR adds a flag in order to select FIPS-enabled GCE or AWS VMs.

* Added `--fips` flag.
* Added wrapper scripts to selectively run FIPS-enabled tests.
* Updated the AWS configs to have an alternative AMIs for FIPS.

Epic: DEVINF-478
Release note: None