Show Run and Debug button when hover on a main method

- When user setting `"java.debug.settings.enableRunDebugCodeLens": true`,  the debugger shows run/debug codelens on top of a main method. 
- When user setting `"java.debug.settings.enableRunDebugCodeLens": false`, the debugger will hide the code lens, but show run/debug button when you hover on a main method.