filodb(core) add debugging info for empty histogram. (#1613)

[yu-shipit]

• filodb(core) add debugging info for empty histogram. Some queries occasionally hit exceptions because of empty histogram. However, the same exception could not be reproduced later. The hunch is that the bug is caused by a race condition. So, adding additional debugging log to print out the chunk id chunk info and the memory dump. ---------

Co-authored-by: Yu Zhang [email protected]
(cherry picked from commit 90303aa)

Pull Request checklist

• The commit(s) message(s) follows the contribution guidelines ?
• Tests for the changes have been added (for bug fixes / features) ?
• Docs have been added / updated (for bug fixes / features) ?

Current behavior : (link exiting issues here : https://help.github.com/articles/basic-writing-and-formatting-syntax/#referencing-issues-and-pull-requests)

New behavior :

BREAKING CHANGES

If this PR contains a breaking change, please describe the impact and migration
path for existing applications.
If not please remove this section.

Breaking changes may include:

• Any schema changes to any Cassandra tables
• The serialized format for Dataset and Column (see .toString methods)
• Over the wire formats for Akka messages / case classes
• Changes to the HTTP public API
• Changes to query parsing / PromQL parsing

Other information: