Move kbn-alert-load tool into Kibana alerting

[mikecote]

This issue is to move the kbn-alert-load tool into Kibana.

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[pmuellr]

for whoever picks this up, I did a quick pass in Dec of moving the package into kibana, here - #84003 . I can't remember what all I had to change, but remember I had to switch out the meow CLI arg parser for whatever we use in Kibana (didn't want to add another dependency).

[mikecote]

@kobelb mentioned that if the versioning of the kbn-alert-load tool isn't the same as Kibana, it's ok to have it in a separate repository. But, if we wanted to couple the tool and Kibana version together, it's ok to integrate with Kibana.

[mikecote]

cc @ymao1 this issue may be something we want to do early in the performance work (#119845).

[ymao1]

I believe @YulNaumenko is working on this.

[EricDavisX]

@EricDavisX tagging himself, may take this over as nobody is working it at this point afaik

[mikecote]

Closing as already completed 🎉