Add tracing spans to last value cache

### Problem statement

There has been variable latency observed when using the last cache under higher concurrent query loads. There are no tracing spans to indicate where in the scan time is being taken, and contributing to that latency, in the last cache.

### Proposed solution

Extract the span context from the DataFusion `Session` that is provided to the `TableProvider::scan` implementation for the `last_cache`: https://github.com/influxdata/influxdb/blob/d8efdb4024749e3d2f05cb8b45e0b721f7cce951/influxdb3_cache/src/last_cache/table_function.rs#L71-L77

It would be worth wrapping a span around the following to generate traces:
* Filter predicate conversion: https://github.com/influxdata/influxdb/blob/d8efdb4024749e3d2f05cb8b45e0b721f7cce951/influxdb3_cache/src/last_cache/table_function.rs#L84-L89
* Record batch conversion: https://github.com/influxdata/influxdb/blob/d8efdb4024749e3d2f05cb8b45e0b721f7cce951/influxdb3_cache/src/last_cache/table_function.rs#L90

Within the latter, we could break down into more spans:
* Predicate evaluation of the cache key hierarchy: https://github.com/influxdata/influxdb/blob/d8efdb4024749e3d2f05cb8b45e0b721f7cce951/influxdb3_cache/src/last_cache/cache.rs#L427-L458
* Scanning the filtered leaf nodes: https://github.com/influxdata/influxdb/blob/d8efdb4024749e3d2f05cb8b45e0b721f7cce951/influxdb3_cache/src/last_cache/cache.rs#L460-L463

### Additional context

This is related to https://github.com/influxdata/influxdb/issues/25562

Start in influxdb3_cache/src/last_cache/table_function.rs at the TableProvider::scan implementation, then read the filter predicate and record batch conversion sections. Follow the related cache.rs sections for cache-key predicate evaluation and filtered leaf scanning. Done means the Session span context is used and tracing spans cover those operations, including the proposed breakdown where useful.

Written by the indexing model from the issue text.