feat: support mixed glob and RegExp arrays in the ignored option

[stormslowly]

Why

Framework authors who wrap watchpack cannot merge their own ignore patterns with the user's when the two use different forms. If a user configures ignored: /\.git/ and the framework wants to append **/dist, there is no value that expresses both: an array is assumed to contain only glob strings, so putting a RegExp in it throws TypeError: Expected a string.

// before — the framework has to hand-build a predicate to combine the two
const userIgnored = /\.git/;
new Watchpack({
  ignored: (item) => userIgnored.test(item) || item.includes("/dist"),
});

// after
new Watchpack({ ignored: [/\.git/, "**/dist"] });

This is the underlying limitation behind web-infra-dev/rspack#10596, where rspack users hit the same wall through watchOptions.ignored.

What

ignoredToFunction now splits an array into glob strings and RegExp instances. Glob strings are still merged into a single RegExp as before; that combined pattern and any user RegExps are then tested against the separator-normalized path.

Ignored becomes (string | RegExp)[] | RegExp | string | IgnoredFunction. Behaviour for string-only arrays, single strings, single RegExps and functions is unchanged.

[changeset-bot]

🦋 Changeset detected

Latest commit: 596dc8c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
watchpack	Minor

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[codspeed]

Merging this PR will not alter performance

✅ 36 untouched benchmarks

---

_{Comparing stormslowly:mixed_ignore (596dc8c) with main (e8ef260)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.19%. Comparing base (e8ef260) to head (596dc8c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #336      +/-   ##
==========================================
+ Coverage   91.91%   92.19%   +0.27%     
==========================================
  Files           8        8              
  Lines        1299     1307       +8     
  Branches      384      385       +1     
==========================================
+ Hits         1194     1205      +11     
+ Misses         99       96       -3     
  Partials        6        6              

Flag	Coverage Δ
integration	92.19% <100.00%> (+0.27%)	⬆️

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