This PR adds support for pluggable client auth providers, which enables pinot components (controller, server, minion) to use dynamically changing tokens, such as kubernetes service account JWTs. The implementation is generic and enables the addition of third-party auth providers to support virtually any environment.

Previously, pinot components were stuck with statically pre-configured client auth tokens. While authentication for the server-side (e.g. restlets responses) was pluggable already, the client-side (e.g. segment fetcher http requests) was configured statically. This would require a full restart of pinot components to address token changes (e.g. rotation). This PR removes this limitation while preserving legacy behavior for static auth.token values, if configured.

Potentially backwards-incompatible changes:

AddTableCommand.setAuthToken() removed (same for other commands)
FileUploadDownloadClient removes several methods specific to auth tokens in favor of header-based method signatures

Release Notes:

Add pluggable auth providers to pinot to enable dynamic client token rotation:

• StaticTokenAuthProvider legacy behavior, job specs
• UrlTokenAuthProvider dynamic file- or url-based token retrieval
• AuthProvider interface for generic third-party implementations

Add support for pinot admin command to inject tokens from a URL using a -authTokenUrl param

New configuration options:
...auth.provider.class provider class name for dynamic loading
...auth.token StaticTokenAuthProvider token, legacy behavior
...auth.url UrlTokenAuthProvider source URL
...auth.prefix StaticTokenAuthProvider and UrlTokenAuthProvider token prefix (typically Basic or Bearer)
...auth.header StaticTokenAuthProvider and UrlTokenAuthProvider http header name (typically Authorization)