[$300 in SQT] Dynamic Datasources destructor

[stwiname]

Now that we have support for Datasource EndBlocks it should be possible for dynamic datasources to remove themselves and set an end blocks.

From within a handler we can inject a function to destroy the current datasource and it should succeed if it is a dynamic datasource.

This would just be an optimisation to simplify dictionary queries and filtering of blocks

Requirements

• 80% test coverage on new code
• Documentation with how to use the feature
• Codegen to generate a named destructor function
• A working example project