Implement value semantics for CosmosClientOptions

[AndriySvyryd]

When the options are provided by the user it would be useful to be able to compare them to each other to be able to return an existing CosmosClient instance if the options used to create it are equivalent.

Describe the solution you'd like
Override Equals and GetHashCode. Using reference equality for options of reference type would be acceptable.

Describe alternatives you've considered
Currently EF accomplishes this by wrapping all the options: https://github.com/dotnet/efcore/blob/38dc78fcc3bfff413cb9ad8a7080dc13a1ca8ee4/src/EFCore.Cosmos/Infrastructure/Internal/CosmosDbOptionExtension.cs#L642