ActiveContext: reload on change and other minor updates

What does this MR do and why?

Adds two new methods:

• collection.name_without_prefix: needed for running the drop_collection migration inline
• connection.adapter which can be run using an active or inactive connection. This is needed to run cleanup if a connection is deactivated.

Also reloads the adapter when a connection is saved. This is to ensure we always use the adapter with the right connection and options.

References

• [ActiveContext Code] Add button to disable sema... (#582787)
• ActiveContext: invalidate current adapter activ... (#521434)

How to set up and validate locally

• Create a connection, activate it and run migrations
• Test that ActiveContext.adapter.connection.collections.first.name_without_prefix is code
• Test that connection.adapter returns the right adapter and options
• Deactivate the connection: connection.deactivate!
• Test that connection.adapter still returns the right adapter and options
• Create a new connection and activate it
• Test that ActiveContext.adapter.connection is the new connection

MR acceptance checklist

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