…stic#33727)

The date_histogram accepts an interval which can be either a calendar
interval (DST-aware, leap seconds, arbitrary length of months, etc) or
fixed interval (strict multiples of SI units). Unfortunately this is inferred
by first trying to parse as a calendar interval, then falling back to fixed
if that fails.

This leads to confusing arrangement where `1d` == calendar, but
`2d` == fixed.  And if you want a day of fixed time, you have to
specify `24h` (e.g. the next smallest unit).  This arrangement is very
error-prone for users.

This PR adds `calendar_interval` and `fixed_interval` parameters to any
code that uses intervals (date_histogram, rollup, composite, datafeed, etc).
Calendar only accepts calendar intervals, fixed accepts any combination of
units (meaning `1d` can be used to specify `24h` in fixed time), and both
are mutually exclusive.

The old interval behavior is deprecated and will throw a deprecation warning.
It is also mutually exclusive with the two new parameters. In the future the
old dual-purpose interval will be removed.

The change applies to both REST and java clients.

…tervals_7x

Due to the fallthrough logic, DateIntervalWrapper assumed that an
otherwise unparsable interval was a legacy fixed millis interval. This
could then NPE if the interval was just illegal ("foobar").

This commit correctly checks if the legacy millis parsing fails too,
and throws an IllegalArgumentException at that point signaling the
provided interval is bad.

The Max Bucket test can potentially return a partial response,
where one of the shards suceeds but another fails due to the max_bucket
setting.  In the case of a partial failure, the status code is 200 OK
since some results were returned (with failures listed in the body).

This makes the yaml test fail since it is expecting a 4xx/5xx failure
when catching exception messages.

We need to disallow partial results so that the entire query fails
and we can check for the max_bucket failure.

Original PR missed documentation for the new calendar/fixed
intervals.  This adds the missing documentation

…tervals_7x