sp_BlitzFirst: more Azure SQL DB performance diagnostics

[BrentOzar]

Is your feature request related to a problem? Please describe.
I've had a couple of underpowered Azure SQL DB clients recently, and I wanna make it easier to see at a glance if they're having failovers or if they're hitting resource limit throttling at the database layer or the elastic pool layer.

Describe the solution you'd like
Pull some diagnostics from these DMVs - just doing a brain dump while I have the data handy:

To be added:

• SELECT TOP 100 * FROM sys.dm_database_engine_configurations
• SELECT TOP 100 * FROM sys.dm_db_resource_stats
• SELECT TOP 100 * FROM sys.dm_database_replica_states
• SELECT TOP 100 * FROM sys.dm_elastic_pool_resource_stats
• SELECT TOP 100 * FROM sys.dm_os_memory_health_history
• SELECT TOP 100 * FROM sys.dm_resource_governor_resource_pools_history_ex
• SELECT TOP 100 * FROM sys.dm_resource_governor_workload_groups_history_ex
• SELECT TOP 100 * FROM sys.dm_user_db_resource_governance
• SELECT TOP 100 * FROM sys.elastic_pool_resource_stats_ex
• SELECT TOP 100 * FROM sys.event_log_ex
• SELECT TOP 100 * FROM sys.resource_stats_raw
• SELECT TOP 100 * FROM sys.resource_usage

Done in other issues:

• SELECT TOP 100 * FROM sys.dm_cloud_database_epoch - useful for determining metrics start time
• SELECT TOP 100 * FROM sys.dm_db_wait_stats - already in use

Are you ready to build the code for the feature?
Yep! I won't do this right away, but will gradually build it in over the next few weeks. After that, I'll also add sp_BlitzFirst to the Consultant Toolkit (to replace the wait stats sampling that we're currently doing in there.)