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/codeql.test.ts

@@ -4,12 +4,12 @@ import * as toolcache from "@actions/tool-cache";
 import test from "ava";
 import nock from "nock";
 
-import { Mode, setMode } from "./actions-util";
 import * as codeql from "./codeql";
 import * as defaults from "./defaults.json";
 import { getRunnerLogger } from "./logging";
 import { setupTests, setupActionsVars } from "./testing-utils";
 import * as util from "./util";
+import { Mode, initializeEnvironment } from "./util";
 
 setupTests(test);
 
@@ -24,7 +24,7 @@ const sampleGHAEApiDetails = {
 };
 
 test.beforeEach(() => {
-  setMode(Mode.actions);
+  initializeEnvironment(Mode.actions, "1.2.3");
 });
 
 test("download codeql bundle cache", async (t) => {
@@ -371,14 +371,14 @@ test("getExtraOptions throws for bad content", (t) => {
   );
 });
 
-test.only("getCodeQLActionRepository", (t) => {
+test("getCodeQLActionRepository", (t) => {
   const logger = getRunnerLogger(true);
 
-  setMode(Mode.actions);
+  initializeEnvironment(Mode.actions, "1.2.3");
   const repoActions = codeql.getCodeQLActionRepository(logger);
   t.deepEqual(repoActions, "github/codeql-action");
 
-  setMode(Mode.runner);
+  initializeEnvironment(Mode.runner, "1.2.3");
 
   // isRunningLocalAction() === true
   delete process.env["GITHUB_ACTION_REPOSITORY"];