dotnet dev-certs should be able to export to a pfx without a password

[jackmtpt]

Is your feature request related to a problem? Please describe.

You can export to .pem/.key files with --no-password but this fails for a PFX file. PFX files can be generated without a password so there's no reason not to allow this.

Describe the solution you'd like

PFX export should be the same as PEM.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.