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/codeql.test.ts

@@ -26,12 +26,14 @@ const sampleApiDetails = {
   auth: "token",
   url: "https://github.com",
   apiURL: undefined,
+  registriesAuthTokens: undefined,
 };
 
 const sampleGHAEApiDetails = {
   auth: "token",
   url: "https://example.githubenterprise.com",
   apiURL: undefined,
+  registriesAuthTokens: undefined,
 };
 
 let stubConfig: Config;