* fix(otel): bound and shut down credential-scoped tracer providers
Each credential-scoped TracerProvider owns a BatchSpanProcessor worker thread that
only stops on shutdown, and the v1 cache holding them was an unbounded, unsynchronized
dict that never shut anything down. Every distinct team/key credential set therefore
added a thread for the life of the process, and concurrent first-requests for the same
credential set orphaned duplicate providers outright.
Make the cache a lock-guarded bounded LRU that shuts down whatever it drops, matching
the v2 TenantTracerCache. Providers wrapping a caller-supplied SpanExporter instance
share that exporter with the logger's own provider, so they are dropped without
shutdown; those use SimpleSpanProcessor and own no thread.
* fix(otel): reclaim dropped providers on a dedicated executor
Sustained credential churn queues one blocking shutdown per eviction, so using the
shared logging executor let an unreachable tenant endpoint stall unrelated logging
work behind the OTLP retry budget. Give provider shutdown its own bounded pool; its
threads spawn lazily, so a proxy that never evicts still pays nothing.
* fix(otel): decide provider shutdown from the victim, not the evicting request
Both dynamic entry points share one provider cache, so it can hold providers of
mixed exporter ownership. Reading the ownership flag from the evicting request
therefore stopped a shared caller-supplied exporter in one direction, silencing
telemetry process-wide, and leaked a BatchSpanProcessor thread in the other.
Cache ownership alongside the provider so the drop decision reads the victim's
own flag.
* fix(otel): honor the widened header mapping type instead of dict only
Widening the header parameter to Mapping left the isinstance check on dict, so a
non-dict Mapping silently returned no headers at all, which for the OTLP path means
an unauthenticated exporter and no traces with nothing raised. The dict branch also
returned the caller's own object, and dropping the defensive copy at the call site
let that alias reach a long-lived exporter. Match on Mapping and copy.
* fix(otel): do not give a provider we may never stop an interpreter-exit hook
Every TracerProvider registers an atexit hook by default, and that hook holds a strong
reference. Providers wrapping a caller-supplied exporter are dropped without shutdown,
so they stayed pinned for the life of the process and then stopped the shared exporter
at exit. Tie shutdown_on_exit to ownership: those providers use SimpleSpanProcessor and
buffer nothing, so they lose no flush, while providers that own their exporter keep the
hook and their exit flush.
Also stop the victim the eviction test leaves behind, and trim the added comments.
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