Build latest Onionperf from git sources

Build latest Onionperf from git sources or from commit reference specified in a variable, instead of using the Debian package from irl's repo.

Trac:
Parent Ticket: #32725 (moved)

added component::metrics/cloud owner::acute parent::32725 priority::medium severity::normal status::needs-revision type::defect labels

Trac:
Parent: N/A to #32725 (moved)

Trac:
Status: new to needs_review

Trac:
Status: needs_review to merge_ready

Trac:
Status: merge_ready to assigned
Owner: metrics-team to acute

https://github.com/torproject/metrics-cloud/pull/2

Trac:
Status: assigned to needs_review
Reviewer: N/A to irl

The paths that things are installed to don't align between the onionperf role and onionperf-webserver role. We probably want things that look like:

/srv/onionperf.torproject.net/onionperf -> onionperf clone
/srv/onionperf.torproject.net/onionperf/onionperf-data -> www root
/srv/onionperf.torproject.net/tgen -> tgen clone

Trac:
Reviewer: irl to N/A
Status: needs_review to needs_revision

Now ready for review at: https://github.com/torproject/metrics-cloud/pull/5

mentioned in issue #32725 (moved)