[1.7.x] Add Trigger for LRTs Post PR

[scottarnette]

Change Description

Added functionality to .cicd/generate-pipeline.sh:

• New trigger for LRTs.
  • Builds triggered by merging a PR into master/develop/release branches now have a step that asynchronously triggers a new pipeline: eosio-lrt.
  • This ensures that eosio PRs are not blocked by LRTs, but still ensures they run after a PR is merged.
  • Functionality remains unchanged non-PR or PR builds. You may still specify LRTs to run via SKIP_LONG_RUNNING_TESTS=false when creating a new build.
  • This trigger will run LRTs only against pinned builds.
  • This pipeline reuses artifacts from the eosio job that triggered it. Resources are not wasted to rebuild the same branch/commit on triggered builds.
  • The eosio-lrt pipeline can be used on its own. SKIP_BUILD is only provided to generate-pipeline.sh if the pipeline was triggered from another pipeline.

See:
Build 17501 | This PR's build.
Build 564 | This PR's unpinned build.
Build 49 | Manual build on eosio-lrt that would build EOS since it was not triggered.
Build 17494 | Post PR build on develop that triggered the LRT and Multiversion pipelines.

Consensus Changes

• Consensus Changes

API Changes

• API Changes

Documentation Additions

• Documentation Additions