perf(scanner,test): speed up language tests (lazy DB, short-circuit, smaller fixtures)

[gheyderov]

What’s in this PR

• Lazy CVE DB: Initialize CVEDB only when binary checkers are used (language-only scans don’t create a DB).
• Language short-circuit: If the filename is a known language fixture (e.g., pom.xml, package-lock.json, PKG-INFO), skip the expensive file-type subprocess checks and call parse(...) directly.
• Smaller fixtures: Shrink test/language_data/fail_pom.xml and fail-package-lock.json to minimal valid samples; behaviour unchanged (these are none_found tests).

Before vs After (on my machine)

• test_language_package_none_found (fail_pom.xml): 0.18s → 0.13s

Notes

• No functional changes; assertions remain identical.
• Checker loading is cached; DB is now lazy; language path avoids subprocess calls.
• Closes test: improve performance on our slowest tests #4321

[gheyderov]

Hi 👋, this PR is part of Hacktoberfest.
If it looks good, could you please add the hacktoberfest-accepted label or review it? 🙏
Thanks!

[terriko]

I don't think this PR actually does what your comment above says, but it looks harmless so I've set the tests to run anyhow.