PC-8075 Updates to MessageDispatch Libraries

[ChrisF-Pharmaxo]

The MessageDispatch library needed to be updated to use the latest version of KurrentDB to reference the Event Store GRPC client.. The work was primarily done in this library, with additional work being done in this PR: qphl/MessageDispatch.ProtobufSnapshotting#11

Work done as part of PC-8075

• Renamed EventStore names to Kurrent.
• Renamed eventstore folder to MessageDispatcher.KurrentDB
• Added C# code styles / formatting
• Updated packages.
• Changed Corsham references to Pharmaxo.
• Updated Subscription logic to reflect the way KurrentDB advises implementing it in their current documents: https://docs.kurrent.io/clients/grpc/subscriptions.html#handling-subscription-drops.
• Multi-targetting .NET 4.8.1 and .NET 8
• Adding test coverage to the library (Todo)

Ticket: https://qphl.atlassian.net/browse/PC-8075

[JoshPattie]

Just one comment. I think this has been thoroughly reviewed at this point!