[RFE] Set custom metric-profiles from flag

[rsevilla87]

Is your feature request related to a problem? Please describe.

With the current implementation, each workload has predefined a metric-profile (metrics.yml, metrics-aggregated.yml, metrics-egress.yml, etc), it would be useful to allow the user to use an external metric-profile

Describe the solution you'd like

A metric-profile list can be passed as a flagThat metric profile can be passed from a flag, i.e:

 ./bin/amd64/kube-burner-ocp cluster-density-v2 --iterations=10 --metrics-profile=custom-metrics.yml,more-metrics.yml

If this flag is not set, kube-burner will follow the previous behavior, of using the pre-defined embedded metrics-profile of the workload in question.

Describe alternatives you've considered

As part of this effort, we can end up deprecating the flag --profile-type, that would mean that the files specified by --metrics-profile can also be embedded in the kube-burner-ocp binary

Additional context

Having this PR can help to fix issues like the one that is trying to fix with #103, which basically is extending the default metrics profile with not relevant prometheus expresions for standards clusters due to the impossibility of using a different metrics-profile rather than the default one.

[vishnuchalla]

@rsevilla87 If we simply deprecate --profile-type flag, it might impact our CI jobs. JFYI.
Also there is a bug: kube-burner/kube-burner#683 which is relevant to this. Hoping that to be fixed as well with this change.