Remove version-probing checks (and old-version support) from dev-tools

[cpcallen]

Category: Plugins

Component: dev-tools

Cleanup to be done:

In the process of doing the goog.module migration of Blockly, it was necessary to add code to dev-tools to probe for various changes that were made in core. Once the next release (end of 2021Q3) of Blockly is out these can be removed.

Describe the solution you'd like:

• In plugins/dev-tools/package.json:
  • Bump required version of blockly as appropriate (e.g. "blockly": "^5.202109__._")
• In plugins/dev-tools/src/index.js:
  • Remove probe for Blockly.utils.global.globalThis (and always use it) (see fix: Change how dev-tools adds Blockly to the global scope for console debugging #881).
• In plugins/dev-tools/src/block_test_helpers.mocha.js:
  • In runSerializationTestSuite, remove probe for Blockly.utils.idGenerator; always stub Blockly.utils.idGenerator.TEST_ONLY (see Use new location for genUid on Blockly.utils.idGenerator #876)