refactor(.github/workflows): reorganize many builds (#332)

1. reduce the number of periodic builds

2. just build as part of the release process in most cases

3. shorttests duplicates coverage

Preliminary changes as part of https://github.com/ooni/probe/issues/1466

.github/workflows/miniooni.yml

@@ -1,15 +1,18 @@
 # miniooni checks whether we can build the research client miniooni
-# and publishes all linux binaries as artefacts. There is no point in
+# and publishes the linux binaries as artefacts. There is no point in
 # publishing windows or darwin binaries b/c they are not signed.
 name: miniooni
 on:
   push:
+    branches:
+      - "release/**"
 jobs:
   test:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
       - run: ./make --disable-embedding-psiphon-config -t miniooni
+
       - run: ./CLI/linux/amd64/miniooni --yes -nNi https://example.com web_connectivity
 
       - uses: actions/upload-artifact@v1