Add an overload to UseCosmos that takes a connection string

[Marusyk]

Add an overload to UseCosmos that takes a connection string.

Fixes #20712

For now, I have some problems with testing it. Could you please suggest if I'm on the right way? I'll continue to work on tests.

[AndriySvyryd]

General approach looks good. You can put the tests in a new class similar to https://github.com/dotnet/efcore/blob/bde2b140d6f4cf94d6d1285d402941e20193ec60/test/EFCore.SqlServer.FunctionalTests/ConnectionSpecificationTest.cs

[AndriySvyryd]

@Marusyk Are you still planning to work on this during June?

[Marusyk]

Yes, but I have a blocker. I cann't run the CosmosDB emulator on my PC.. So, I cann't add tests

[AndriySvyryd]

@Marusyk Uninstall and reinstall the emulator, then right-click on the task bar icon and select "Reset Data...". If it still doesn't work then add the tests blindly and I'll fix them if necessary.

[Marusyk]

Add an overload that takes a single string rather than the URI and the key
It seems we cannot use a single string parameter because we also need to specify the database name.

The connection string to CosmosDB doesn't contains Database name

AccountEndpoint=https://localhost:8081/;AccountKey=C2y6yDjf5/R+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw/Jw==

@AndriySvyryd

should I add something like:
UseCosmos(string connectionString, string database)

[AndriySvyryd]

should I add something like:
UseCosmos(string connectionString, string database)

Yes, all overloads should have the Database name parameter

[Marusyk]

Added only one test for now.
Not sure about changes in GetServiceProviderHashCode and PopulateDebugInfo methods from CosmosOptionsExtension file.

[Marusyk]

Could you please help with the build? Don't understand what's wrong, I got "Build succeeded." on the local machine.

[AndriySvyryd]

@Marusyk Rebase your changes on latest master

[AndriySvyryd]

Squash the commits

[AndriySvyryd]

@Marusyk Thanks for your contribution!