Remove simple explain and refactor explain

[shahzadlone]

We currently have:

@explain
@explain(type: execute)
@explain(type: debug)
@explain(type: simple)

• We want to remove the explicit simple explain as the default should do the basic explain stuff.
• Remove all type arguments.

Instead we want to have:

@explain

• Returns simple explain with all explainable nodes and their attributes.

@explain(debug: true)

• Returns simple explain with all explainable nodes and their attributes
• With extra internal nodes.

@explain(execute: true)

• Returns simple explain with all explainable nodes and their attributes
• With additional execute metrics for all explainable nodes.

@explain(execute: true, debug: true)

• Returns simple explain with all explainable nodes and their attributes
• With additional execute metrics for all explainable nodes.
• With extra internal nodes.

Ability to hide attributes

@explain(execute: true, debug: true, hideAttributes: true)

• Returns simple explain with all explainable nodes (without their attributes).
• With additional execute metrics for all explainable nodes.
• With extra internal nodes.

@explain(debug: true, hideAttributes: true)

• Returns simple explain with all explainable nodes (without their attributes).
• With extra internal nodes.

@explain(execute: true, hideAttributes: true)

• Returns simple explain with all explainable nodes (without their attributes).
• With additional execute metrics for all explainable nodes.

@explain(hideAttributes: true)

• Returns simple explain with all explainable nodes (without their attributes).