Support builds-on/runs-on arm

[addyess]

Adding a builds-on/runs-on arm64 section for each charm

• Each architecture will have a unique charm for the eventual some-day when we need binary bits in the charms
• Build each architecture with GH builders

[addyess]

worker charm can specify it's requirements.txt so that the python reqs can be installed with no-binary

[mateoflorido]

LGTM

[addyess]

NOW this PR depends on merging of this PR in order to get multiarch builds back

• build on configurable architecture operator-workflows#313

[addyess]

thanks to @arturo-seijas and @weiiwang01 for unblocking this

[github-actions]

Test coverage for c4f6647

coverage-report: install_deps /home/runner/work/k8s-operator/k8s-operator/charms/worker/k8s> python -I -m pip install 'coverage[toml]'
coverage-report: commands[0] /home/runner/work/k8s-operator/k8s-operator/charms/worker/k8s> coverage report
Name                                    Stmts   Miss  Cover
-----------------------------------------------------------
lib/charms/k8s/v0/k8sd_api_manager.py     265     26    90%
src/charm.py                              442    231    48%
src/containerd.py                         140     16    89%
src/cos_integration.py                     33     12    64%
src/reschedule.py                          77      4    95%
src/snap.py                                79      3    96%
src/token_distributor.py                  165     92    44%
-----------------------------------------------------------
TOTAL                                    1201    384    68%
coverage-report: OK (1.17=setup[0.99]+cmd[0.17] seconds)
congratulations :) (1.22 seconds)

Static code analysis report

Run started:2024-10-30 22:31:33.697076

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 2714
  Total lines skipped (#nosec): 14
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 0

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):

[addyess]

I did some study on a failure on ARM now that we're testing with lxd VMs.

lxd is required to use /dev/kvm, but on ARM64 -- /dev/kvm may not exist. I even logged into the machine and tried to add sudo modprobe kvm but it fails to load the kernel mode.

without /dev/kvm -- lxd doesn't start the machines and the tests fail

Therefore -- this change allows for lxd-containers on ARM -- but i expect we'd need arm64 to support /dev/kvm or don't use lxd as a cloud for arm64