feat: Add ssh client to run-task so git clones through SSH (bug 1989234)

[JohanLorenzo]

For reference, the latest build didn't include openssh-client:

The following additional packages will be installed:
 [...]
Suggested packages:
 [...]
Recommended packages:
 [...] openssh-client [...]
The following NEW packages will be installed:
  ca-certificates curl git git-man libbrotli1 libcurl3-gnutls libcurl4
  liberror-perl libexpat1 libgdbm-compat4 libgdbm6 libgssapi-krb5-2
  libk5crypto3 libkeyutils1 libkrb5-3 libkrb5support0 libldap-2.5-0
  libncursesw6 libnghttp2-14 libnsl2 libperl5.36 libpsl5 libpython3-stdlib
  libpython3.11-minimal libpython3.11-stdlib libreadline8 librtmp1 libsasl2-2
  libsasl2-modules-db libsqlite3-0 libssh2-1 libssl3 libtirpc-common libtirpc3
  media-types mercurial mercurial-common openssl perl perl-modules-5.36
  python3 python3-distutils python3-lib2to3 python3-minimal python3-pip
  python3-pkg-resources python3-setuptools python3-wheel python3.11
  python3.11-minimal readline-common sensible-utils sudo ucf unzip
0 upgraded, 55 newly installed, 0 to remove and 0 not upgraded.

https://firefox-ci-tc.services.mozilla.com/tasks/TW54TrRfTFOUpB3ysHWLAw/runs/0/logs/public/logs/live.log

[jcristau]

Could we use https with a token instead?

[JohanLorenzo]

What are the pros of HTTPS compared to SSH?

[jcristau]

It'd be the same path as everything else, and token permissions can hopefully be more fine-grained.

[JohanLorenzo]

I agree it would make easier to have one way to deal with repos. Who will own the token?

One good thing about SSH is that we can use deploy keys in read-only mode. They're set up at the repo level. So they're not tied to any account.