Remove uses of EncryptPEMBlock

Created by: camdencheek

We have some limited use of x509.EncryptPEMBlock, which has recently been deprecated due to security issues. As the PR description points out, there is currently no good alternative.

Are use of it is very limited and would be difficult to exploit since we never hand out the encrypted private key or the passphrase, but we should find a way to migrate away from the deprecated function to avoid future uses that may be more vulnerable.