Resolve export * as ns re-exports under modern parsers

[rasmi]

Fixes two pre-existing ExportAllDeclaration bugs that affect modern parsers (espree ES2020+, @babel/eslint-parser) but not babel-eslint. Extracted from #3230 (eslint v10 support) to make that PR cleaner.

Root cause

babel-eslint represents export * as ns from './mod' as ExportNamedDeclaration + ExportNamespaceSpecifier (a working code path), so the bug was latent. Modern parsers emit ExportAllDeclaration with exported, which hit two broken spots:

• specifier.js: passed a string (specifier.source.value) to namespace.add(), which expects an AST node — so the namespace getter was never set up and ns didn't resolve. Fixed by defining the lazy getter directly, matching the existing ExportNamespaceSpecifier case.
• visitor.js: export * as ns was unconditionally added to the star-export dependencies set, incorrectly flattening the target module's exports into the current one. Fixed by only adding to dependencies for plain export * (no as).

Tests

The included regression test covers the false negative: the namespace rule now correctly flags invalid deep references through export * as re-exports that were previously silently missed (fails on main, passes with the fix).

The false-positive symptoms #1834, #1883, #1845, #2002, #2289 ("errors after upgrading Babel") are resolved by the same change, but only reproduce with @babel/eslint-parser, which is introduced in #3230.

Fixes #2002, #1883, #1834, #1845, #2289.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.66%. Comparing base (395dfc9) to head (15dcddd).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3250      +/-   ##
==========================================
+ Coverage   95.50%   95.66%   +0.16%     
==========================================
  Files          83       83              
  Lines        3693     3692       -1     
  Branches     1336     1334       -2     
==========================================
+ Hits         3527     3532       +5     
+ Misses        166      160       -6     

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