test(linter/plugins): add conformance tests (#16650)

Add conformance tester for JS plugins.

The tester runs all of ESLint's test cases for all its built-in rules, but using Oxlint's `RuleTester` in place of ESLint's. i.e. the ESLint rules are run as Oxlint JS plugins.

It outputs the results in `snapshot.md` file.

Majority of the failing test cases are false positives. Later PRs will improve the conformance tester and `RuleTester` so it correctly handles `sourceType`, `jsx`, and TypeScript sources.

These tests do not run in CI. For now it's just useful for me to commit this, while I work on improving the tester.

I'm not sure if inside `apps/oxlint` is the right place for this ultimately, but for now I think it's passable.

Author: overlookmotel

.typos.toml

@@ -6,6 +6,7 @@
 extend-exclude = [
   "**/*.snap",
   "**/*/CHANGELOG.md",
+  "apps/oxlint/conformance/snapshot.md",
   "crates/oxc_linter/fixtures",
   "crates/oxc_linter/src/rules/eslint/no_unused_vars/ignored.rs",
   "crates/oxc_linter/src/rules/eslint/no_unused_vars/options.rs",

apps/oxlint/conformance/.gitignore

@@ -0,0 +1 @@
+submodules

apps/oxlint/conformance/README.md

@@ -0,0 +1,29 @@
+# Oxlint JS plugins conformance tests
+
+Conformance tests run all ESLint's tests for its built-in rules as Oxlint JS plugins.
+
+They do this by substituting ESLint's `RuleTester` for Oxlint's version, and then `require()`ing the ESLint test files
+to run the tests.
+
+The results are saved in `conformance/snapshot.md`.
+
+## Setup
+
+Build Oxlint in debug mode:
+
+```sh
+cd apps/oxlint
+pnpm run build-test
+```
+
+Initialize ESLint submodule:
+
+```sh
+pnpm run init-conformance
+```
+
+## Run conformance tests
+
+```sh
+pnpm run conformance
+```

apps/oxlint/conformance/init.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+set -e
+
+ESLINT_SHA="e593aa0fd29f51edea787815ffc847aa723ef1f8"
+
+# Delete existing `submodules` directory
+rm -rf submodules
+
+# Clone ESLint repo into `submodules/eslint`
+git clone --single-branch --depth 1 https://github.com/eslint/eslint.git submodules/eslint
+cd submodules/eslint
+git fetch --depth 1 origin "$ESLINT_SHA"
+git reset --hard "$ESLINT_SHA"
+git clean -f -q
+
+# Install dependencies
+pnpm install --ignore-workspace
+
+# Copy TS-ESLint parser shim into `node_modules/@typescript-eslint/parser`
+rm node_modules/@typescript-eslint/parser
+cp -r tools/typescript-eslint-parser node_modules/@typescript-eslint/parser
+cd node_modules/@typescript-eslint/parser
+
+# Install dependencies of TS-ESLint parser shim
+pnpm install --ignore-workspace