Use new EventArgs of onDidChangeConfiguration to determine what settings changed

[DonJayamanne]

Make use of the eventargs of onDidChangeConfigurationEvent to determine what changed and accordingly act on this.
Currently we do do check what changed, and if we do, we perform our own comparisons to determine if there are any changes.

• client/common/configSettingMonitor.ts
• client/interpreter/display/shebangCodeLensProvider.ts#L9
• client/unittests/main.ts#L237

[luabud]

Seems to be merged.