CLOUDP-126267: Add 'Upgrade One Shared Tier Cluster' endpoint to atlas go client

[Razeer123]

Description

I added "Upgrade One Shared Tier Cluster" endpoint to Atlas Go Client, and a test to check the correctness of the implementation.

How to use the endpoint

After creating a cluster that we want to upgrade, the upgrade request should be sent to the following endpoint: https://cloud-dev.mongodb.com/api/atlas/v1.0/groups/{GROUP-ID}/clusters/tenantUpgrade. In the body of the request, there should be an upgraded cluster object. Example body:

{
    "name": "tenantCluster",
    "diskSizeGB": 100,
    "numShards": 1,
    "providerSettings": {
    "providerName": "AWS",
    "instanceSizeName": "M40",
    "regionName": "US_EAST_1"
    },
    "clusterType" : "REPLICASET",
    "replicationFactor": 3,
    "replicationSpecs": [{
    "numShards": 1,
    "regionsConfig": {
        "US_EAST_1": {
        "analyticsNodes": 0,
        "electableNodes": 3,
        "priority": 7,
        "readOnlyNodes": 0
        }
    },
    "zoneName": "Zone 1"
    }],
    "backupEnabled": false,
    "providerBackupEnabled" : true,
    "autoScaling": {
    "diskGBEnabled": true
    }
}

On success, the endpoint should return 200 code with entity containing the result of the upgrade.

Type of change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Required Checklist:

• I have signed the MongoDB CLA
• I have added tests that prove my fix is effective or that my feature works
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code