[ui/public/utils] Delete unused base_object & find_by_param

[lukeelmers]

Part of #51560

There are a few utils in src/legacy/ui/public/utils that appear to be unused in Kibana:

• Double-check that base_object is unused, and delete it @alexwizp [[ui/public/utils] Delete unused base_object & find_by_param #52500]
• Double-check that find_by_param is unused, and delete it @alexwizp [[ui/public/utils] Delete unused base_object & find_by_param #52500]
• Delete any corresponding unit tests @alexwizp [[ui/public/utils] Delete unused base_object & find_by_param #52500]
• Document both changes in the ui/public cleanup section of the dev docs issue Dev Docs entry: ui/public & angular cleanup 7.6 #43511

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)