Remove backend predicate results from audience evaluation

[tonidero]

Motivation

The backend is dropping the backend_predicate_results item from the audiences remote-config topic, so the SDK no longer needs to read it or expose it to rule evaluation.

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Note

Medium Risk
Changes how checkpoint and audience rules resolve when predicates still reference backend.* (those reads are no longer supplied), which can shift match outcomes until dashboard rules are updated.

Overview
Aligns the SDK with the backend removing the backend_predicate_results item from the audiences remote-config topic.

Audiences config no longer bundles pre-evaluated backend predicates with the audience blob: AudiencesSnapshot and getSnapshot() are gone in favor of getAudiences(), which only loads the default audiences blob under a consistent config generation.

Local rules evaluation drops the reserved backend.* dimension scope—LocalRulesEvaluator and RulesDimensionResolver no longer accept backendValues, and checkpoint audience matching passes only custom variables plus audience predicates. Subscriber dimensions from the customer response remain as root-level names (unchanged).

Tests that covered backend predicate matching and metadata parsing were removed or updated to match the slimmer API.

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