[Cosmos DB] [API Review] Move to azcore 0.20 and fit and finish

[ealsur]

This PR covers finishing touches from the API Review. The major changes:

Remove of Cosmos prefix

Removing Cosmos prefix from pending APIs.

Move to azcore 0.20.0

Allows embedding policy.ClientOptions and reduce pipeline initialization code. azcosmos.ClientOptions were greatly reduced.

Closes #15818

Item content

Aligning with other Go SDKs, the operations that take an item payload (like container.CreateItem) now take the raw []byte as input, giving users the freedom to choose the serialization method and technology of their choice and removing serialization from inside the SDK code for user data.

Closes #15819

PartitionKey

To be more clear about the expectations and reduce error checking, NewPartitionKey(interface{}) (*PartitionKey, error) has been removed and 3 explicit constructors exist that cover the 3 types:

• NewPartitionKeyBool(bool): For any boolean partition key
• NewPartitionKeyString(string): For any string partition key
• NewPartitionKeyNumber(float64): For any number (int, float, etc) partition key

None of these return errors, so it's simpler from the user perspective.

Retry on 429

We remove our policy in favor of the azcore policy which already retries on 429s.

Renames

Several method renames, among them, the relevant are:

• client.GetContainer -> client.NewContainer to be more idiomatic
• client.GetDatabase -> client.NewDatabase to be more idiomatic
• database.GetContainer -> client.NewContainer to be more idiomatic
• Container -> ContainerClient to align with other Go SDKs for grouping Container level operations
• Database -> DatabaseClient to align with other Go SDKs for grouping Database level operations
• Id -> ID
• ResourceId -> ResourceID

Other public API refactorings

• Removed UnixTime, _ts is not returned as int64
• Any int was changed to either int32 or int64