Added Execution Frame Subclasses

[TeodorDjelic]

What changes were proposed in this pull request?

Changes proposed are the refactoring of SqlScriptingExecutionFrame class. Instead of using an enum to encompass the frame type, class hierarchy was added added to the SqlScriptingExecutionFrame base class, and for every subtype a new class was added.

New class hierarchy:

SqlScriptingExecutionFrame
|
*--------------------------------------------------------\
|                                                        |
SqlScriptingHandlerExecutionFrame            SqlScriptingSqlScriptExecutionFrame
|
*---------------------------------------------------------------\
|                                                               |
SqlScriptingExitHandlerExecutionFrame         SqlScriptingContinueHandlerExecutionFrame

Why are the changes needed?

Refactor was done for increased code robustness and clarity. Also, it loses at least a field per execution frame object.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

It was tested using existing tests, to retain old behavior.

Was this patch authored or co-authored using generative AI tooling?

No.