Use the latest Httpclient/Httpcore 5.x in HBase

HttpClient 4.x is not actively developed.

We use Httpclient directly in the REST client code, and in the tests for several modules.

Httpclient 4.5 is a transitive dependency at least from Hadoop and Thrift, but httpclient 5.x uses a separate java package, so 4.5 and 5.x should be able to co-exist fine.

As of now, Httpclient 4.5 is in maintenance mode:
https://hc.apache.org/status.html