[Traceql Metrics] PR 3 - Trace ID sharding

[mdisibio]

What this PR does:
This PR implements the trace-ID sharding used by metrics in the block Fetch() method. For context: the query-frontend divides a metrics query into jobs along 2 dimensions: horizontally across time (i.e. a job every 5 minutes) and vertically across trace IDs (i.e. 10 shards). This PR is the vertical scaling. For example: shard "10 of 16" processes only traces A00.... through AFF.... This is done with a predicate against the TraceID column.

There are some other details to be aware:

• Some tricks to shard both 8-byte and 16-byte trace IDs.
• It uses the previously-experimental trace ID index json in each block. This eliminates quite a few reads because we can go straight to the row groups that contain the matching trace IDs instead of testing every one. I think we fixed the issues with index, it's been working well for me.

Notes
This is one entry in a set of chained PRs. The full body of work has been split into separate buckets to make reviews and updates more manageable.

1. [Traceql Metrics] PR 1 - Engine #3251
2. [Traceql Metrics] PR 2 - API #3252
3. [Traceql Metrics] PR 3 - Trace ID sharding #3258

Which issue(s) this PR fixes:
Fixes #

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[zalegrala]

This looks good to me. Nice work.