Add support for 64-bit unsigned integers

[jpountz]

As a follow-up to discussions in #17006, we agreed in FixitFriday to add support for 64-bit unsigned integers. These numbers will support accurate term and range queries, but aggregations will work on the nearest double value.

[elasticmachine]

Pinging @elastic/es-search-aggs

[rw-access]

Just adding this note here for reference.

We ran into a use case for this in elastic/ecs#673. The Windows registry only has a concept of unsigned numbers, so we saw two paths to take for numbers greater than 2⁶³ for u64. We either cast to s64, which is hard to enforce and too easy to do wrong. The other option was to only store the string representation. Since we have little need for math, we opted for a keyword string field in the interim.

[marshallmain]

Following up on @rw-access comment, there are a fair number of data fields coming from the Elastic Endpoint that we would like to store as u64 if possible. Is this issue being actively worked on?

[ktetzlaff]

Same problem here during processing of network performance data from routers as part of a network management system. This data contains counters (e.g. received octets) which are 64-bit unsigned values. It would be great if we could store them properly.