fix: improved scratch org create authentication

[shetzel]

What does this PR do?

1. The signupTargetLoginUrl override used in sfdx-project.json files was not used for scratchOrgResumes, causing auth code exchange issues during resume. It is now used.
2. encrypts the client secret written to the scratch-create-cache.json file.
3. If the auth code exchange fails when using a loginUrl that differs from ScratchOrgInfo.LoginUrl another attempt is made using ScratchOrgInfo.LoginUrl.
4. Improves debug logging for the loginUrl used during the auth code exchange

What issues does this PR fix or reference?

@W-16825003@

To QA:

• use a devhub with another connected app that has a consumer secret and use it to create scratch orgs. Ensure the clientSecret value written to the cache file is encrypted.
• resume a scratch org create where the signupTargetLoginUrl is necessary and ensure that login URL override is used for the auth code exchange.
• check that another attempt is made if the auth code exchange fails with the first loginUrl if that loginUrl doesn't match ScratchOrgInfo.LoginUrl.

[shetzel]

None of the existing tests could possibly fail since result is a stubbed return setup by the tests. I added expectations that should have been there from the start, as well as a few additional checks for the new code I added.