Add environment variables to signal feature and version to the CLI

This PR ensures environment variables are set before any invocation of
the CLI.  Here is a list of vars that are set:

https://github.com/github/codeql-coreql-team/issues/1124#issuecomment-852463521

This ensures the CLI knows the features and versions of the containing
actions/runner.

Additionally:

- Fix the user agent so that it more closely aligns with user agent
  spec
- Refactor environment variable initialization so that it all happens in
  one place and call.
- Move Mode, getRequiredEnvParam, setMode, getMode out of actions-util
  and into util. actions-util is meant for utils only called by the
  action, not the runner.

The `prepareLocalRunEnvironment()` method is most likely deprecated and
should be removed. I originally added it because I had a way of working
where I would run the action from my local machine to test out changes,
but this was always a little flaky. So, I no longer use this way of
working. I will probably remove it soon.

src/upload-lib.test.ts

@@ -3,16 +3,21 @@ import * as path from "path";
 
 import test from "ava";
 
-import { Mode, setMode } from "./actions-util";
 import { getRunnerLogger } from "./logging";
 import { setupTests } from "./testing-utils";
 import * as uploadLib from "./upload-lib";
-import { GitHubVersion, GitHubVariant, withTmpDir } from "./util";
+import {
+  initializeEnvironment,
+  Mode,
+  GitHubVersion,
+  GitHubVariant,
+  withTmpDir,
+} from "./util";
 
 setupTests(test);
 
 test.beforeEach(() => {
-  setMode(Mode.actions);
+  initializeEnvironment(Mode.actions, "1.2.3");
 });
 
 test("validateSarifFileSchema - valid", (t) => {