feat(napi/parser): add AST walker

[overlookmotel]

Add an AST visitor to oxc-parser.

import { parseSync, Visitor } from 'oxc-parser';

const { program } = parseSync('test.js', 'let x = { y: z };');

const idents = [];
const visitor = new Visitor({
  Identifier(node) {
    idents.push(node.name);
  }
});

visitor.visit(program);

// Logs [ 'x', 'y', 'z' ]
console.log(idents);

Primarily we need a visitor for Oxlint plugins, but it's easier to develop and test in oxc-parser, so I thought I'd add it there first. Oxlint build process will copy the generated files for tree-walking from napi/parser dir, as it does with other files.

Notes:

• The walk.mjs file is large, so it's lazy-loaded only when user first constructs a Visitor. Adding Visitor to the package will not affect start-up time where user only uses parseSync etc.
• TS type definition for Visitor and the visitor object it takes are provided.
• Visitor supports enter and exit visitors e.g. Program and Program:exit.
• src-js/visit/visitor.mjs is copied from apps/oxlint with only minor modifications, and conversion from TS to JS. It'd be better if we only had this impl in one place, but that would require converting oxc-parser to TS and building with TSDown, like oxlint is. Leaving that for later - Convert oxc-parser to TypeScript #13935.

[overlookmotel]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(linter/plugins): add defineRule API #13945
• feat(linter/plugins): add createOnce API #13944
• feat(linter/plugins): ESTree-compatible AST for JS plugins #13942
• feat(napi/parser): add deserializeProgramOnly deserializer function #13940
• feat(napi/parser): add AST walker #13930 👈 (View in Graphite)
• feat(napi/parser): export visitor keys #13927
• fix(napi/parser): raw transfer preserveParens option apply to TSParenthesizedType #13964
• main

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