This commit adds the commands used to generate the various RSA keys to tests/Makefile so that they can be easily
regenerated or modified, e.g. if larger key sizes or other encryption algorithms need to be tested in the future.
With SHA-1 deprecation, we need a few certificates using algorithms in
the default support list. Most tests still use SHA-1 though.
The generation process for the new certificates is recorded in the makefile.
