refactor: integrate more probe-engine workflows (#204)

This diff is part of https://github.com/ooni/probe/issues/1335.

We are moving more probe-engine workflows to toplevel.

The general idea here is to migrate all possible workflows and to
delete the ones that we cannot use in this repo (if any).

internal/engine/.github/workflows/alltests.yml

@@ -1,16 +0,0 @@
-name: alltests
-on:
-  push:
-    branches:
-      - 'release/**'
-  schedule:
-    - cron: "0 7 * * */1"
-jobs:
-  test:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/setup-go@v1
-        with:
-          go-version: "1.14"
-      - uses: actions/checkout@v2
-      - run: go test -race -tags integration,shaping -coverprofile=probe-engine.cov ./...