fix: TemplateStore eviction cleanup, error reporting, and doc accurac…

[mikemiles-dev]

…y (1.0.4)

• AutoScopedParser source eviction now clears the evicted parser's templates from the store before drop (prevents monotonic keyspace growth in long-running multi-tenant deployments).
• clear_v9_templates / clear_ipfix_templates record template_store_backend_errors on remove failures (previously swallowed via let _ = ...).
• Honest doc comment on clear_*_templates in-LRU-only semantics.
• set_template_store_scope / with_template_store_scope rustdoc warnings about scope-change orphan windows and AutoScopedParser overrides.
• template_store_restored doc clarifies hit-not-miss semantics and TTL re-stamping behavior.

Tests:

• Rewrote vacuous read_through_drives_pending_flow_replay to actually queue a pending flow before any template is known, then verify read-through restores the template AND replays the queued flow.
• Strengthened auto_scoped_parser_uses_per_source_scope with a cross-replica round-trip read-through assertion.
• New tests: AutoScopedParser eviction store cleanup, clear_*_templates backend-error counting, IPFIX codec corruption, IPFIX LRU eviction propagation, IPFIX TemplateEvent::Restored firing.
• inject_remove_failures is no longer dead code.

Example:

• New horizontal_scale_out_template_store example demonstrates two parser replicas sharing an InMemoryTemplateStore — replica A learns and goes away, replica B starts cold and decodes via read-through.