Contribute qdrant java client

[russcam]

This PR contributes a java client for qdrant.

• Gradle is used for build automation. Easy to extend with additional tasks, and fast for incremental builds.
• A Custom gradle task downloads protos from qdrant/qdrant, based on version specified in properties, which can be passed by commandline. No need to check in versioned protos, and protos are auto patched to include java package name.
• Project is configured with No nulls by default, NullAway, Errorprone, enforcement of JavaDocs.
• Ability to pass a channel to the client. This allows users to configure channel credentials however they need to for their environment e.g. self-signed certs for TLS, proxies, etc.
• Ability for the client to manage the lifetime of the channel. A singleton instance of the client would typically be created, and Spring Boot is a popular choice for DI. Being able to configure the client to shutdown the channel on close is useful, as Spring can take care of it.
• Exposes async methods that return ListenableFuture which can be composed to form concurrent operations, or called and waited on with .get(), optionally with a timeout.
• Exposes ability to set an overall default timeout for all calls, and optionally provide a timeout per call.
• Client is configured with logging, all calls are debug logged, and all exceptions are error logged.
• Overloaded methods for common operations. Some operations have many parameters that are optional, so the builder types are used.

[Anush008]

Thank you so much for the amazing contribution ❤️

I'll open PRs with some additions. Would really appreciate your reviews there.