[analytics-plugin] Dsl percentiles agg

[sachin-27]

Description

Adds support for the percentiles metric aggregation (t-digest) to the DSL Calcite plugin.
Stacks on #22561 — only the last commit is new to this PR.

Key changes:

• PercentilesMetricTranslator: translates percentiles to PERCENTILE_APPROX aggregate calls (one per requested percent), honoring percents, missing, and format
• t-digest compression via a three-argument PERCENTILE_APPROX_N form, registered across the analytics framework function enum, the engine's literal-argument planning rule, and the DataFusion backend (rewriter + function catalog)
• InternalDslPercentiles: renders the classic tdigest_percentiles response shape, including typed_keys
• hdr method is rejected at conversion (analytics path supports t-digest only)

Check List

• [x ] Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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