Add support for downloading packs from GHES

This change adds:

- new `registries` block allowed in code scanning config file
- new `registries-auth-tokens` input in init action
- Change the downloadPacks function so that it accepts new parameters:
    - registries block
    - api auth
- Generate a qlconfig.yml file with the registries block if one is
  supplied. Use this file when downloading packs.
- temporarily set the `GITHUB_TOKEN` and `CODEQL_REGISTRIES_AUTH` based
  on api auth

TODO:

1. integration test
2. handle pack downloads when the config is generated by the CLI

src/runner.ts

@@ -203,6 +203,7 @@ program
         externalRepoAuth: auth,
         url: parseGitHubUrl(cmd.githubUrl),
         apiURL: undefined,
+        registriesAuthTokens: undefined,
       };
 
       const gitHubVersion = await getGitHubVersion(apiDetails);
@@ -479,6 +480,7 @@ program
         auth,
         url: parseGitHubUrl(cmd.githubUrl),
         apiURL: undefined,
+        registriesAuthTokens: undefined,
       };
 
       const outputDir =
@@ -592,6 +594,7 @@ program
       auth,
       url: parseGitHubUrl(cmd.githubUrl),
       apiURL: undefined,
+      registriesAuthTokens: undefined,
     };
     try {
       const gitHubVersion = await getGitHubVersion(apiDetails);