* ci: delete legacy required-checks shim workflow
* ci: fold semgrep into lint and helm into unit, drop the duplicate UI build
semgrep runs the repo's own rules over the source, so it becomes lint / semgrep
behind lint passed. The helm chart tests become unit / helm behind unit passed.
UI Build Check ran the same docker build --target ui-builder as
smoke / dashboard-build, so it is deleted
* ci: merge the alphabetical llms shards into one llms-providers shard
The two shards were split by letter range, which says nothing about what they
run. Every provider without its own shard now runs in llms-providers, with the
same 137 paths as before
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Co-authored-by: yuneng <yuneng@berri.ai>