build: ignore vararg-overload Revapi check for dependency archives #1285

Since #1053 replaced the blanket ignore of java.method.varargOverloadsOnlyDifferInVarargParameter with reportUnchanged: false, any new vararg overload in any dependency archive fails Full verify. #1274 (blockhound 1.0.17) was the first hit; #1284 excludes reactor.blockhound only.

Other dependencies already carry such overloads (counts from #1117): jackson-databind (48, compile scope, bumped regularly by Renovate) and gremlin (52, optional). The next bump that adds one breaks CI the same way. A package exclusion can't cover Jackson, because ObjectMapper is driver API (ExtraTypeCodecs.json).

Proposal (untested): one ignore in the root pom's revapi.ignore, scoped to dependency archives:

{
  "code": "java.method.varargOverloadsOnlyDifferInVarargParameter",
  "newArchiveRole": "supplementary",
  "justification": "Vararg overloads in third-party dependencies are not driver API"
}

Acceptance:

• With the reactor.blockhound exclusion removed, mvn -pl core revapi:check passes on blockhound 1.0.17.
• A vararg overload added to driver code is still reported.

Refs: #1117, #1284, #1053