Let deploy.py fail verbosively if jsonnet - golang version - isn't on path

[consideRatio]

Its a hidden requirement, lets fail explicitly.

Actually, I think we require jsonnet from the golang project specifically since #90 was merged upgrading grafonnet to version 10.4.0 - so we should check for that.

Failure from using c++ based jsonnet (version 0.17.0 I think):

RUNTIME ERROR: field does not exist: get
	vendor/grafonnet/custom/util/././panel.libsonnet:112:22-29	object <anonymous>
	vendor/grafonnet/custom/util/././panel.libsonnet:220:18-33	function <func>
	std.jsonnet:789:24-47	thunk <running>
	std.jsonnet:789:9-57	function <aux>
	std.jsonnet:789:9-57	function <aux>
	std.jsonnet:790:5-28	function <anonymous>
	vendor/grafonnet/custom/util/././panel.libsonnet:([21](https://github.com/2i2c-org/infrastructure/actions/runs/8660326053/job/23748043528#step:7:22)6:5)-(228:6)	function <anonymous>
	vendor/grafonnet/custom/util/./grid.libsonnet:74:25-101	thunk <uncollapsed>
	vendor/grafonnet/custom/util/./grid.libsonnet:76:45-56	thunk <panels>
	vendor/grafonnet/custom/util/././panel.libsonnet:[25](https://github.com/2i2c-org/infrastructure/actions/runs/8660326053/job/23748043528#step:7:26)0:31-37	
	...
	vendor/grafonnet/clean/../custom/./util/./panel.libsonnet:57:12-18	thunk <panels>
	vendor/grafonnet/clean/../custom/./util/./panel.libsonnet:54:9-15	thunk <arr>
	std.jsonnet:790:15-18	thunk <arr>
	std.jsonnet:786:28-31	
	std.jsonnet:786:17-32	function <aux>
	std.jsonnet:790:5-28	function <anonymous>
	vendor/grafonnet/clean/../custom/./util/./panel.libsonnet:(21:7)-(56:8)	function <infunc>
	vendor/grafonnet/clean/../custom/./util/./panel.libsonnet:57:5-19	function <anonymous>
	vendor/grafonnet/clean/../custom/dashboard.libsonnet:[27](https://github.com/2i2c-org/infrastructure/actions/runs/8660326053/job/23748043528#step:7:28):12-48	object <anonymous>
	During manifestation	
Traceback (most recent call last):
  File "/home/runner/work/infrastructure/infrastructure/grafana-dashboards/./deploy.py", line 205, in <module>
    main()
  File "/home/runner/work/infrastructure/infrastructure/grafana-dashboards/./deploy.py", line 200, in main
    deploy_dashboard(dashboard, args.folder_uid, api)
  File "/home/runner/work/infrastructure/infrastructure/grafana-dashboards/./deploy.py", line 72, in deploy_dashboard
    db = build_dashboard(dashboard_path, api)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/infrastructure/infrastructure/grafana-dashboards/./deploy.py", line 58, in build_dashboard