[Fix] no-unresolved: handle template literal requires

[pratyushsinghal7]

What changed

Treat no-substitution template literals passed to CommonJS require() as static module paths in moduleVisitor.

The template's cooked string value is exposed on a shallow source-node copy, so existing resolution logic and visitor-based rules can consume it without mutating the parser AST. Template literals containing expressions remain dynamic and are ignored.

Regression coverage verifies that:

• require(`./bar`) resolves successfully.
• require(`./baz`) reports import/no-unresolved.
• Both the node and webpack resolver test configurations exercise the cases.

Fixes #1575.

Validation

• BABEL_ENV=test ./node_modules/.bin/mocha --require babel-register tests/src/rules/no-unresolved.js --reporter dot — 157 passing
• npm test — full tests, ESLint, generated documentation checks, and Markdown lint passed

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.60%. Comparing base (ee005b6) to head (950393e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3276      +/-   ##
==========================================
+ Coverage   79.57%   79.60%   +0.02%     
==========================================
  Files          98       98              
  Lines        4539     4545       +6     
  Branches     1537     1572      +35     
==========================================
+ Hits         3612     3618       +6     
  Misses        927      927              

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[pratyushsinghal7]

CI baseline note: the failing Tests: eslint (old versions) matrix is unchanged from main. The latest main run at https://github.com/import-js/eslint-plugin-import/actions/runs/29535690274 and this PR run each have the same 50 failing jobs (the Node 10–15 / ESLint 2–6 combinations), while all 194 other matrix jobs pass.

The focused rule test also passes locally with npm run mocha -- tests/src/rules/no-unresolved.js. The old-version matrix failures appear to be pre-existing dependency/runtime failures rather than failures introduced by this two-file change.

[ljharb]

this is a good fix, but i hope nobody's actually using no-substitution template literals anywhere

(added additional test coverage)