chore(build): remove the dead -Xelide-below scalac option

[aglinxinyuan]

What changes were proposed in this PR?

Removes -Xelide-below WARNING from the sixteen build.sbt files that set it, along with the comments that exist only to explain it. Build-config only, 16 files, −20 lines, no behaviour change.

⚠️ Stacked on #7451. The first commit here is #7451's deletion of ElidableStatement; it drops out of this diff once #7451 merges. The order is required — see Why the order matters below. Review the second commit, chore(build): remove the dead -Xelide-below scalac option.

Why the flag is dead

-Xelide-below <level> makes scalac replace a call to an @elidable(n) method with () when n < level. The only @elidable-annotated code in this repo was ElidableStatement:

Wrapper	Level	vs. WARNING (900)
finest	FINEST 300	compiled out
finer	FINER 400	compiled out
fine	FINE 500	compiled out
info	INFO 800	compiled out

It had no callers, so nothing was actually being elided, and #7451 deletes it. After that git grep -in elidable is empty and the flag switches nothing.

Why this is a no-op, not a silent re-enable

The obvious worry is assert. It is @elidable(ASSERTION) = 2000, above WARNING, so assertions are compiled in today — and scalac's default with -Xelide-below absent elides nothing, so they are compiled in after this too. Same for assume. Nothing that was elided starts running, and nothing that was running stops.

Why the order matters

Dropping the flag while ElidableStatement still exists would break ElidableStatementSpec, which asserts counter == 0 after ElidableStatement.info { counter += 1 } — true only under elision. Hence the stack rather than a standalone PR.

What was removed

Thirteen modules share one line; three differ:

File	Removed
amber/build.sbt	the whole scalacOptions ++= Seq(...) line + the // to turn on, use: INFO / // to turn off, use: WARNING pair above it
common/workflow-compiler/build.sbt	two Seq entries (flag and value on separate lines)
computing-unit-managing-service/build.sbt	one Seq entry
the other thirteen	one Seq entry each, with its // Turn on optimizations with "WARNING" as the threshold trailing comment

Full list: access-control-service, amber, common/{auth,config,dao,pybuilder,resource,util,workflow-compiler,workflow-core,workflow-operator}, computing-unit-managing-service, config-service, file-service, notebook-migration-service, workflow-compiling-service.

Any related issues, documentation, discussions?

Closes #7706

Follow-up to a review note from @Yicong-Huang on #7451.

How was this PR tested?

Existing tests only — this is a build-config removal, and there is nothing left to test once the one construct the flag governed is gone.

Locally, from the repo root with Java 17:

• sbt compile Test/compile over the root aggregate (all sixteen modules) — success.

Verification, re-runnable by a reviewer:

git grep -in xelide      # nothing
git grep -in elidable    # nothing

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Generated-by: Claude Code (Claude Opus 5)

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Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @kz930, @Ma77Ball, @Yicong-Huang
  You can notify them by mentioning @kz930, @Ma77Ball, @Yicong-Huang in a comment.