Use metadata cache for performance (Get-DataverseEntityMetadata)

[rnwood]

Demonstrates the performance improvement when using the metadata cache.

# First call - fetches from server
Measure-Command { $metadata1 = Get-DataverseEntityMetadata -EntityName contact -UseMetadataCache }

# Milliseconds : 450

# Second call - uses cache
Measure-Command { $metadata2 = Get-DataverseEntityMetadata -EntityName contact -UseMetadataCache }

# Milliseconds : 2