Upgrade ESLint to v9 and its related plugins to their latest major version

[Patel-Raj11]

Following are the changes introduced by this PR:

1. Upgrade ESLint to v9 and now exports Flat configs that were first introduced in v8.21.0 of ESLint.
2. Upgrade various ESLint plugins used by this shared config to their latest major version and account for their breaking changes.
3. Add V2_MIGRATION.md file to list the migration steps and breaking changes.
4. Update typescript-style repo itself to use Flat configs (i.e. use eslint.config.js file) for it's own linting.
5. Update README with installation and usage guide for @xrplf/eslint-config@2.0.0.

Following are the changes that are expected in xrpl.js and VHS to consume @xrplf/eslint-config@2.0.0 once it's released.

1. XRPLF/xrpl.js@main...eslint-v9-migration
2. ripple/validator-history-service@main...eslint-v9-migration

[Copilot]

Pull Request Overview

This PR upgrades ESLint to version 9 and migrates the configuration to use Flat Config format, which is the new configuration system introduced in ESLint v8.21.0. The migration includes upgrading ESLint plugins to their latest major versions and converting the entire configuration structure from the legacy format to the new flat configuration format.

Key Changes:

• Upgraded ESLint from v8 to v9 and migrated all rule configurations to use Flat Config syntax
• Updated all ESLint plugins to their latest major versions (eslint-plugin-import, eslint-plugin-jsdoc, etc.)
• Converted configuration files from legacy .eslintrc.js format to eslint.config.js flat configuration format

Reviewed Changes

Copilot reviewed 32 out of 35 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/eslint-config/package.json	Updated peer dependencies to ESLint v9 and latest plugin versions
packages/eslint-config/rules/*.js	Converted all rule configuration files from legacy to flat config format
packages/eslint-config/base.js	Restructured base configuration to use flat config array format
packages/eslint-config/index.js	Updated main entry point to export flat config arrays
packages/eslint-config/eslint.config.js	Added flat configuration file for the package itself
packages/eslint-config/V2_MIGRATION.md	Added migration guide documenting breaking changes
packages/eslint-config/README.md	Updated documentation with flat config usage examples

Comments suppressed due to low confidence (2)

packages/eslint-config/rules/@typescript-eslint.js:1

• [nitpick] The caughtErrors: 'none' setting disables validation of catch block arguments, which could lead to unused error variables. Consider changing to 'all' and uncommenting the caughtErrorsIgnorePattern to maintain consistency with the pattern of requiring underscore prefixes for unused variables.

/* eslint-disable max-lines, max-len -- Required here due to many overrides */

packages/eslint-config/rules/@typescript-eslint.js:1

• [nitpick] The TODO comment indicates uncertainty about the allowDirectConstAssertionInArrowFunctions setting. This should be resolved by either setting it to true with justification or removing the comment if false is the intended value.

/* eslint-disable max-lines, max-len -- Required here due to many overrides */

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