Add read timeout for getting records when sampling a stream

[zachjsh]

Description

Previously, when sampling streaming data, the sampler would wait timeoutMs for numRows to be returned. If the stream has less rows than numRows, the sampler would wait the full timeoutMs period. In some cases, initially connecting to a given stream to sample may take a considerable amount of time, but reading subsequent records thereafter is a much faster operation. For these cases, this PR adds a new sampler config property readTimeoutMs, which if specified, causes the sampler to return after this period of time if no further records are found between the last record found, or timeoutMs, whichever comes first. The new readTimeoutMs is only applied once some records have been read from the stream during sampling. For example if a stream has only 1 record in it at a given time, and timeoutMs is configured as 15000 miliseconds and readTimeoutMs is configured as 2000 milliseconds while numRows is configured as 500, then assuming the first record is read quickly, the sampler will return after roughly 2000 milliseconds, whereas previously it would have returned after the full 15000 millesecond timeoutMs config value.

This PR has:

• [x] been self-reviewed.
  • [ ] using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• [ ] added documentation for new or modified features or behaviors.
• [ ] a release note entry in the PR description.
• [x] added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• [ ] added or updated version, license, or notice information in licenses.yaml
• [ ] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• [x] added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• [ ] added integration tests.
• [x] been tested in a test Druid cluster.