Fix for claims and client capabilities JSON merge bug in net6

[gladjohn]

Fixes : #4447

Identified a bug in MSAL's JSON merging logic affecting applications targeting .NET 6 and above. JSON objects with properties of the same name but different structures are not merged correctly, leading to data loss

// JSON 1
"access_token": {
    "xms_cc": {
        "values": ["cp1", "cp2"]
    }
}

// JSON 2
"access_token": {
    "nbf": {
        "essential": true,
        "value": "1701540593"
    }
}

problem : After merging, xms_cc is lost, retaining only the nbf property.

fix : This fix ensures that JSON merging is performed correctly, avoiding data loss when properties have the same name but different structures. The implementation considers various value kinds (objects, arrays) and recursively merges nested structures. It addresses the identified issue and provides a reliable merging mechanism for JSON objects.

Testing : Unit tests and manual verification that we pass capabilities now in net6.

Other notes : Unit tests also has coverage for net48 that uses newtonsoft code path, and we do not have this issue in that code path

[bgavrilMS]

Approve, but I agree with Peter's comment