CI: Specify project id and masterbranch manifest, add variable for the ci rev

* The master branch manifest needs to be specified here, as the kirkstone branch
includes the same files and needs to use kirkstone as master branch
manifest
* The project id needs to be specified here, as the 'manifest.yml' will
be included in multiple manifest repos with different ids.
* Putting the gitlab-ci-rev into a variable allows it to use it in
further ci steps. The 'deploy-gitlab-cy' step of the gitlab-ci repo
should update this value as well, as a plain substitution of the hash is
used.

Change-Id: I5d7996edee4d0b94d0365424b0db44449cefabd1

.gitlab-ci.yml

@@ -6,3 +6,8 @@ include:
   - project: '${CI_PROJECT_ROOT_NAMESPACE}/yocto/infrastructure/gitlab-ci'
     ref: e6980d48ee67bafe2049ca9d36820070bc1479d1
     file: 'manifest.yml'
+
+variables:
+  MANIFEST_PROJECT_ID: 1725
+  MASTER_BRANCH_MANIFEST: dunfell
+  GITLAB_CI_CURRENT_REV: e6980d48ee67bafe2049ca9d36820070bc1479d1