refactor jest setup to improve unit/integration test executions (#2322)

* fix test:integration command to run tests directly under ./test/integration

* refactor jest setup to have separate config files for integration and unit tests

packages/xrpl/jest.config.unit.js

@@ -0,0 +1,13 @@
+// Jest configuration for api
+const base = require('../../jest.config.base.js')
+
+module.exports = {
+  ...base,
+  roots: [...base.roots, '<rootDir>/test'],
+  testMatch: ['<rootDir>/test/**/*.test.ts'],
+  testPathIgnorePatterns: [
+    '<rootDir>/test/integration',
+    '<rootDir>/test/fixtures',
+  ],
+  displayName: 'xrpl.js',
+}