3167 pluralize credential collectors

[ilija-lazoroski]

What does this PR do?

Fixes part of #3167 .

PR Checklist

• Have you added an explanation of what your changes do and why you'd like to include them?
• Is the TravisCI build passing?
• Was the CHANGELOG.md updated to reflect the changes?
• Was the documentation framework updated to reflect the changes?
• Have you checked that you haven't introduced any duplicate code?

Testing Checklist

• Added relevant unit tests?
• Do all unit tests pass?
• Do all end-to-end tests pass?
• Any other testing performed?

  Tested by {Running the Monkey locally with relevant config/running Island/...}

• If applicable, add screenshots or log transcripts of the feature working

[cakekoa]

I see that tests pass. Looks like we still have a package named infection_monkey.credential_collectors

[ilija-lazoroski]

I see that tests pass. Looks like we still have a package named infection_monkey.credential_collectors

Those are going to be removed really soon.

[shreyamalviya]

BB test configurations need to be changed

[shreyamalviya]

For Mimikatz too

Suggested change

	class SSHCredentialCollector(ICredentialsCollector):
	class SSHCredentialsCollector(ICredentialsCollector):

But I guess we could skip this since they're going to be migrated to plugins soon.

[mssalvatore]

+1 for skipping for now.