[Internal] Thin Client Integration: Adds diagnostic log info for thinclient mode.

[aavasthy]

Pull Request Template

Description

• Updated the Diagnostics Summary to contain the proxy interactions:

   "Summary": {
       "GatewayCalls": {
           "(200, 0)": 1,
           "(304, 0)": 1
       },
       "GatewayV2Calls": {
           "(200, 0)": 1
       }
  

• Added a new feature in the UserAgentFeatureFlags the following, so that the diagnostics user agent can contain the
  thin client enablement flag:

  • A new Feature Flag for Thin Client.
  • A new Feature Flag for Binary Encoding.

   	internal enum UserAgentFeatureFlags
   	{
   		 PerPartitionAutomaticFailover = 1,
  
                       PerPartitionCircuitBreaker = 2,
  
                       ThinClient = 4,
  
                       BinaryEncoding = 8,
   	}	
  

  An updated user agent can look like the following: "User Agent": "cosmos-netstandard-sdk/3.51.0|1|X64|Microsoft Windows 10.0.26100|.NET 6.0.36|L|F4|" if only thinclient is enabled.

• New feature (non-breaking change which adds functionality)

Closing issues

To automatically close an issue: closes #4615

[kundadebdatta]

Change it to ProxyCalls ?

[aavasthy]

Let's keep thinclient across, thinclient is the mode name and summary has details about different mode names.

[kirankumarkolli]

ThinClient in diagnostic naming feels not right. At=least syntactically ThinProxy might be right mapping.
Might be even better to have an abstract notion (like GWV2 etc...) thoughts?

[kundadebdatta]

Yes - ThinProxy sounds better.

[kundadebdatta]

Closing this PR as the follow up PR PR-5265 has been merged with only the user agent feature changes.

We can re-open this PR in the future if needed.