[FEATURE] Make Authorization and Token endpoints configurable  #251

Problem Statement
The SDK currently has fixed logic to "discover" the OAuth endpoints based on host or account_id specified in the config. This limits the flexibility for the user to specify which OAuth service they want to use for the authentication.

Proposed Solution
The SDK Config class should have an optional parameter for specifying oidc_endpoints. If this parameter is not specified, the current logic for discovering the endpoints should be used. If this is specified these endpoints should be used for U2M and M2M flows instead of discovering the endpoints.

Additional Context
There are few customers that have custom OAuth configuration. Even other customers who are on Azure and GCP may want to have flexibility to use the Azure/GCP OAuth providers or the Databricks native OAuth providers. Related issue: databricks/databricks-sdk-py#595