build(docs-infra): display github links in CLI API docs (#26515)

This commit includes the following changes:

* CLI version information is read from the CLI package from which
  we read the help files.
* CLI API pages now contain GH links
* line numbers are not shown in GH links, if the doc does not
  have a truthy `startingLine` value. This allows us to remove
  hard coded checks for `guide` pages
* content pages and CLI api docs no longer have a `startingLine`
* the hard-coded `packages` path segment has been removed from
  the templates; instead we now only use the `realProjectRelativePath`.
* the `realProjectRelativePath` has been updated accordingly for API
  and CLI API docs.

PR Close #26515

aio/tools/transforms/angular-api-package/processors/fixupRealProjectRelativePath.js

@@ -0,0 +1,14 @@
+module.exports = function fixupRealProjectRelativePath(API_DOC_TYPES) {
+  return {
+    $runAfter: ['readTypeScriptModules'],
+    $runBefore: ['processing-docs'],
+    $process(docs) {
+      docs.forEach(doc => {
+        if (API_DOC_TYPES.indexOf(doc.docType) !== -1 && doc.fileInfo && doc.fileInfo.realProjectRelativePath) {
+          // this is an API doc - so fix up its real path
+          doc.fileInfo.realProjectRelativePath = 'packages/' + doc.fileInfo.realProjectRelativePath;
+        }
+      });
+    }
+  };
+};