* Boilerplate for new context menu options
* Enables checkmarks for expensive operator context menu actions
* Updates azdataGraph version to 0.0.44
* Adds clearing logic to actions and retrieves additional info from nodes
* Removes unnecessary actions that aren't supported by other providers
* Finishes setting up the rest of the context menu actions
* Corrects context menu action label
* Defines new widget type for finding expensive operations
* Adds TODO for class icon name
* Creates action to open the expensive operation widget
* Adds escape and enter key shortcuts to findExpensiveOperation widget
* Styles find expensive operation widget
* Corrects class name for finding expensive operator action
* Corrects import statement.
* Code clean up
* Bumps azdataGraph version to 0.0.45
* Adds an info box for when a metric doesn't find any nodes
* Adds label to find expensive operator widget
* Invokes dispose when widget controller removes widget
* Implements disposable in all execution plan widgets.
* Adds off action to clear highlighting
* Adds a default setting and default prompt for highlighting metric
* Fixes not all code paths return error
* Removes shortcut key from text for widget actions
* Adds enum description
* Removes added dictionary type, and renames class name
* Removes unnecessary null checks
* Removes cost metric dictionary and adds corresponding properties
* Code review changes
* Removes incorrectly implemented key down event for widget.
* Renames widget and action class names for highlighting expensive ops
* File rename
* Cleans up labels to better reflect highlight action
* Removes hardcoded button width style and sets it to auto
* More clean up
* Clean up import statement
* Code review changes
* Drop down list only shows available metrics
* Updates highlight expensive operation icon
* Update STS version
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