[exporter/doris] Report rows filtered out by Doris during a successful stream load

[vedatkilic]

Description

With max_filter_ratio > 0, Doris may drop up to that fraction of rows from a batch and still return Status: Success — the loss is only visible in the stream load response's NumberFilteredRows field, which the exporter parsed but never inspected (success() checks Status only). Today the only trace is log_response: true, which logs every response at INFO and relies on an operator reading them.

This PR surfaces the loss at the moment it happens:

• A shared reportFilteredRows hook called from the logs/traces/metrics push paths: when NumberFilteredRows > 0 on an otherwise successful load it emits a WARN with filtered_rows, loaded_rows, the stream load label, and the Doris error_url (which points at the per-row rejection detail).
• A new otelcol_exporter_doris_filtered_rows monotonic counter (mdatagen telemetry: section; this is the component's first internal metric, so the generated TelemetryBuilder is wired into the common exporter — the per-signal constructors and factory now propagate the builder's error).
• Loads with zero filtered rows stay completely silent: no WARN, no counter points.

Link to tracking issue

Fixes #49011

Testing

• TestPushLogDataFilteredRows: fake stream load endpoint returns Status: Success with NumberFilteredRows: 3; asserts the WARN fields (counts + error URL) via a zap observer and the counter value via metadatatest.AssertEqualExporterDorisFilteredRows.
• TestPushLogDataNoFilteredRowsStaysSilent: clean response produces no WARN.
• Full go test ./... for the module passes; gofmt/go vet clean.
• The failure mode itself was reproduced against a live Doris cluster (3 BE, strict_mode on the load): a malformed row yields Status: Success, NumberLoadedRows: 2, NumberFilteredRows: 1 with no signal anywhere in the collector before this change.

Documentation

• metadata.yaml telemetry entry + regenerated documentation.md describe the new metric.
• Changelog entry added via .chloggen.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: vedatkilic / name: Vedat Kılıç (6fb0ddc)

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