Add CopyableBuilder and ToCopyableBuilder interfaces to the credential providers.

[millems]

Fixes #3129

[cenedhryn]

Looks good, but I don't see any tests

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
4 Code Smells

20.5% Coverage
0.0% Duplication

[millems]

We don't traditionally test the toBuilder methods on any of our builders. Do you think we should test each of these?

[cenedhryn]

I'm a bit surprised about that actually! It's easy to introduce bugs when converting to builder, both when the method is added as well as over time if the instance variables are expanded.

public BaseBuilder(Function<B, T> providerConstructor, StsCredentialsProvider provider) {
            this.providerConstructor = providerConstructor;
            this.asyncCredentialUpdateEnabled = provider.asyncCredentialUpdateEnabled;
            this.stsClient = provider.stsClient;
           // this.staleTime = provider.staleTime;   <-- OOPS forgot to add the stale time here -->
            this.prefetchTime = provider.prefetchTime;
 }

Pretty sure I've seen bugs in similar cases before. You can consider it, it's not a blocker.

[millems]

This was merged as part of #3267