Port remaining components to "Microsoft.Data.SqlClient"

[analogrelay]

• dotnet-sql-cache tool
• SqlConnectionHealthCheck (cc @rynowak) Not a shipping thing, a sample. Never mind.

cc @ajcvickers @divega

[Pilchie]

Assigning since you're looking at this already.

[analogrelay]

Merged #12447 to update to the latest. Leaving this open because we need to update to the RTM build when it's available.

[analogrelay]

#12957 is tracking this now.