bpo-45019: Add a tool to generate list of modules to include for frozen modules (gh-27980)

Frozen modules must be added to several files in order to work properly. Before this change this had to be done manually. Here we add a tool to generate the relevant lines in those files instead. This helps us avoid mistakes and omissions.

https://bugs.python.org/issue45019

.github/workflows/build.yml

@@ -71,6 +71,7 @@ jobs:
           make regen-stdlib-module-names
       - name: Check for changes
         run: |
+          git add -u
           changes=$(git status --porcelain)
           # Check for changes in regenerated files
           if ! test -z "$changes"