fix(#364): run only referenced lints in unlint-non-existing-defect

[VasilevNStas]

Fixes #364

Problem: The unlint-non-existing-defect lint is the slowest one, by an order of magnitude, according to the benchmark. The reason: for every document it ran defects() on all lints, even when the document had no +unlint metas at all.

Solution: The lint now collects the +unlint tails first and, if the document has none, returns an empty result without touching any lint. Otherwise, only the lints whose names are referenced by the +unlint metas are executed, instead of the full set.

Changes:

• src/main/java/org/eolang/lints/LtUnlintNonExistingDefect.java: rewritten defects() to short-circuit on documents without +unlint; existing() filters lints by the referenced names before calling defects().
• src/test/java/org/eolang/lints/LtUnlintNonExistingDefectTest.java: two new tests asserting that no lint runs when there are no +unlint metas and that unreferenced lints are not invoked (a lint that explodes when called would fail the test).

Tests: mvn clean install -Pqulice — 580 tests, all green.

[volodya-lombrozo]

Appreciate the fix! The commits here aren't signed, which rultor requires for merging — details on signing commits are here: https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits. Closing for now; feel free to reopen with signed commits.

[VasilevNStas]

@volodya-lombrozo, fixed — commits are now SSH-signed (verified by GitHub). Since the closed PR can't be reopened after a force-push, I've recreated it as #1233 (same change, signed commits).