Add support for a configurable default segment history period for segmentMetadata queries and GET /datasources/<datasourceName> lookups

[jon-wei]

This is a re-opening of older pull request #1726, addressing the latest comments from @gianm

[fjy]

👍

[nishantmonu51]

I wonder what is the expected behaviour when a user sets both the intervals and userDefaultInterval to true ?
should it throw exception or give priority to useDefaultInterval flag ?

I looks with the current implementation if both are set, it will return results for the interval that spans the configured defaultPeriod period before the end time of the specified interval interval instead of the default interval ?
Is that what is the expected behaviour ?

[gianm]

IMO we should not document usingDefaultInterval, its only purpose is to help "remember" that a user did not specify intervals. Without something like that it's hard to remember, since the querySegmentSpec needs to be filled in with DEFAULT_INTERVAL to allow the later filtering to work.

So I think if a user specifies "usingDefaultInterval" directly that is their own problem and we don't need to provide any particular behavior :)

[gianm]

lgtm with the additional changes