WIP: Use self-hosted runners

[kimwnasptd]

This is a WIP PR to investigate what are the blockers with self-hosted runners

[kimwnasptd]

The tests on self-hosted are currently failing with
ERROR cannot deploy bundle: cannot add relation between "kfp-metadata-writer:grpc" and "mlmd:grpc": no relations found

Trying to understand if the following lines are the root cause
https://github.com/canonical/envoy-operator/blob/76a2cc5fd88e19f134a1bf5056db27c32b2b0e46/metadata.yaml#L24-L27
https://github.com/canonical/mlmd-operator/blob/166957f119924134c95766b2179f28a40abbdb76/metadata.yaml#L15-L30

Which is slightly different from
https://github.com/canonical/minio-operator/blob/9c73db3a2bccccb7a67b4df19dfbbe0e0674854f/metadata.yaml#L19-L47

kfp-operators/charms/kfp-api/metadata.yaml

Lines 26 to 54 in cbd8c58

	object-storage:
	interface: object-storage
	schema:
	v1:
	provides:
	type: object
	properties:
	access-key:
	type: string
	namespace:
	type:
	- string
	- 'null'
	port:
	type: number
	secret-key:
	type: string
	secure:
	type: boolean
	service:
	type: string
	required:
	- access-key
	- port
	- secret-key
	- secure
	- service
	versions: [v1]
	__schema_source: https://raw.githubusercontent.com/canonical/operator-schemas/master/object-storage.yaml

In which the schema is defined by both requirer and provider (maybe self-hosted and the networking have something to do here?)

[kimwnasptd]

Trying to use mlmd and envoy from latest/edge, which is using the library and not SDI. But now the kfp-viz Charm fails to build with the following error:
https://github.com/canonical/kfp-operators/actions/runs/9148235882/job/25150566557?pr=432

::   File "/snap/charmcraft/3454/lib/python3.10/site-packages/charmcraft/charm_builder.py", line 250, in _install_dependencies
::     _process_run([pip_cmd, "install", f"pip@{KNOWN_GOOD_PIP_URL}"])
::   File "/snap/charmcraft/3454/lib/python3.10/site-packages/charmcraft/charm_builder.py", line 408, in _process_run
::     raise RuntimeError(f"Subprocess command {cmd} execution failed with retcode {retcode}")
:: RuntimeError: Subprocess command ['/root/parts/charm/build/staging-venv/bin/pip', 'install', 'pip@https://files.pythonhosted.org/packages/ba/19/e63fb4e0d20e48bd2167bb7e857abc0e21679e24805ba921a224df8977c0/pip-23.2.1.tar.gz'] execution failed with retcode 2
Parts processing error: Failed to run the build script for part 'charm'.
Failed to build charm for bases index '0'.

[DnPlas]

@kimwnasptd are you still working on this PR? If so, please convert it to draft or close it if it is not required anymore.