[google-auth-library-java] Generating ID token with ImpersonatedCredentials does not support overriding quota project

**Is your feature request related to a problem? Please describe.**
`ImpersonatedCredentials` accepts a quota project in its builder, and the quota project is properly overridden when generating an access token. However, when generating id token with the `idTokenWithAudience()` method, it won't perform such override. The impact is that if a service does impersonate many IdTokens on its own quota - it exceeds a default limit of 60k.

**Describe the solution you'd like**
It seems to me that providing the quota project in the `additionalFields` argument when invoking the `IamUtils.getIdToken()` method would work

**Describe alternatives you've considered**
There doesn't seem to be good alternatives.