* [logstash bridge]: stableapi bootstrap
Adds a new `logstash-bridge` project in `/libs` that exports api-stable
wrappers for the elasticsearch-internal types that Logstash's Elastic
Integration Filter relies on to provide ingest pipeline execution inside
of Logstash.
These bridge classes prevent Elasticsearch-internal refactorings from
breaking the Logstash-owned project.
* Update docs/changelog/108171.yaml
* rename StableAPI -> StableBridgeAPI