Now that the jobs are running again, a number of deprecation warnings
have surfaced
https://github.com/libevent/libevent/actions/runs/4876367881:
```bash
Node.js 12 actions are deprecated. Please update the following actions to use Node.js 16: actions/checkout@v2.0.0.
```
Looks like the most straightforward thing todo here is just use the
newer version of the checkout action.
Also move to the v1 tag for the coveralls job, rather than a pinned,
much older version (the latest release is 1.2.5, https://github.com/coverallsapp/github-action/releases).
Same again for actions/cache.
Change made by setting top-level read-only permisisons, and any
other necessary permissions set as job-level.
Closes#1421
Signed-off-by: Diogo Teles Sant'Anna <diogoteles@google.com>
Right now because we have separate workflows there is no one page with
all the jobs, instead we have separate page for each workflow (linux,
windows, ...)
This is pretty inconvenient, so let's make it cleaner, and now we will
have only two:
- for pull requests
- for upstream/master
