feat(Log4Net)!: Support credential type configuration

[robertvoinescu-work]

Added CredentialType to GoogleStackdriverAppender configuration to support credential specification.

BREAKING CHANGE: Credentials now default to service_account type instead of auto-detecting. If using
non-service-account credentials (e.g., authorized_user), you MUST explicitly set the CredentialType
property in your configuration.

[amanda-tarafa]

I have mostly the same questions here regarding the defaults. I know what you've done in code, but I want to make sure that what's done in configuration files is fine as well. Let's chat about it.

[amanda-tarafa]

A few things, but mostly questions. Can you update the documentation as well? Here: https://github.com/googleapis/google-cloud-dotnet/blob/main/apis/Google.Cloud.Logging.Log4Net/docs/configuration.md

Also, apply the relevant changes from this one to the NLog PR, once we get this one merged and all relevant changes done in NLog, I'll review that one. Thanks.

[amanda-tarafa]

Very minor things, it looks good.

[amanda-tarafa]

This is adding the extra line again.

[robertvoinescu-work]

The .editorconfig specifies adding a new line at the end of each file:

My editor must have picked it up and added it in. I might prefer to keep the new line so it's in line with the config, but I can also see a preferences for not introducing these formatting updates into older files. What would you prefer?

[robertvoinescu-work]

I've removed the new line for now.

[amanda-tarafa]

The only thing is apis.json is generated. I don't mind changing what generates it to add the extra blank line, but until we do that, it will be removed even if we add it.