Issue #3678 support value type extended scalars in Strawberry Shake

[retterbot]

Add support for value type scalars

• The current implementation of TypeInfos has a dictionary of type mappings, during the registration phase where scalar extensions are registered it creates new RuntimeTypeInfos but it does not register them. This means that when the schema file itself is processed the extended type information is lost and so all types are registered as non value types as this is the default.
• To resolve this, during the registration phase, the created RuntimeTypeInfo is added to the dictionary.
• The implementation isn't thread-safe I assume this is OK as the calling code runs on a single thread.

Closes #3678

[michaelstaib]

@PascalSenn can you do the review? It should actually already be fixed now but the tests are still useful.

[PascalSenn]

@brian-tygotech Thanks for the contribution ! Timing was a bit unfortunate as this was already resolved in another branch. But the tests are still super helpful!
LGTM