feat: Programmatically Execute Indexer Locally (#908)

This PR sets up a local indexer class which leverages the in memory dml
handler class and a no op indexer meta class to fully execute indexer
logic locally on a block. The class is responsible for downloading block
data and providing helper functions to abstract testing logic away. This
PR also sets up a core-indexers folder which is used to verify that the
created local indexer is actually capable of executing indexer code
locally. The core-indexers folder may be temporary as we do intend to
eventually publish a testing framework npm package. For the time being,
it uses relative imports to work.

core-indexers/.eslintrc.js

@@ -0,0 +1,35 @@
+module.exports = {
+  parser: '@typescript-eslint/parser',
+  env: {
+    es2021: true,
+    node: true
+  },
+  overrides: [
+    {
+      files: ['.eslintrc.js', 'jest.config.js'],
+      parser: 'espree',
+      extends: ['standard'],
+      rules: {
+        semi: ['error', 'always'],
+        quotes: ['error', 'single'],
+        'array-callback-return': ['error', { allowImplicit: false }]
+      }
+    },
+    {
+      files: ['**/*.ts'],
+      parserOptions: {
+        project: './tsconfig.json',
+        tsconfigRootDir: __dirname
+      },
+      extends: [
+        'standard-with-typescript'
+      ],
+      rules: {
+        '@typescript-eslint/semi': ['error', 'always'],
+        '@typescript-eslint/comma-dangle': ['error', 'only-multiline'],
+        '@typescript-eslint/strict-boolean-expressions': 'off',
+        'array-callback-return': ['error', { allowImplicit: false }]
+      }
+    }
+  ]
+};

core-indexers/jest.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  testMatch: ['**/*.test.ts'],
+  testTimeout: 10000
+};