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

lib/util.test.js

@@ -156,6 +156,7 @@ function mockGetMetaVersionHeader(versionHeader) {
         auth: "",
         url: "https://github.com",
         apiURL: undefined,
+        registriesAuthTokens: undefined,
     });
     t.deepEqual(util.GitHubVariant.DOTCOM, v.type);
     mockGetMetaVersionHeader("2.0");
@@ -163,6 +164,7 @@ function mockGetMetaVersionHeader(versionHeader) {
         auth: "",
         url: "https://ghe.example.com",
         apiURL: undefined,
+        registriesAuthTokens: undefined,
     });
     t.deepEqual({ type: util.GitHubVariant.GHES, version: "2.0" }, v2);
     mockGetMetaVersionHeader("GitHub AE");
@@ -170,6 +172,7 @@ function mockGetMetaVersionHeader(versionHeader) {
         auth: "",
         url: "https://example.githubenterprise.com",
         apiURL: undefined,
+        registriesAuthTokens: undefined,
     });
     t.deepEqual({ type: util.GitHubVariant.GHAE }, ghae);
     mockGetMetaVersionHeader(undefined);
@@ -177,6 +180,7 @@ function mockGetMetaVersionHeader(versionHeader) {
         auth: "",
         url: "https://ghe.example.com",
         apiURL: undefined,
+        registriesAuthTokens: undefined,
     });
     t.deepEqual({ type: util.GitHubVariant.DOTCOM }, v3);
 });