* MM-61865: Add mobile client content load network metrics
* added new common label
* renaming from MobileClientContentLoad to MobileClientNetworkRequests
* content_load_group => network_request_group
* refactor more NetworkRequest-* changes
* replace contentLoadGroup to networkRequestGroup
* new metrics elapsedTime
* Refactor urlCount to totalRequests
* add averageSpeed metric
* replace contentLoadGroup with networkRequestGroup
* use h.Labels vs commonLabels for network_request_group
* add agent
* add effective latency metrics
* add total parallel requests & total sequential
* mocks generated by mockery
* did a bit of cleanup and sorting
* formatting
* updated the AcceptedNetworkRequestGroups
* cleanup and sorting