[folding] clicking on on line number of folded line should select full folding range

Issue Type: <b>Bug</b> 1. Fold an area (e.g. a block in JSON) to a line 2. Click the margin of the folded line 3. Try to drag the mouse to select the whole folded area **Expected**: Can select (only) the whole folded area **Actual**: It's either the first line of folded area, or the whole folded area **and** next line. Other editors do not have this problem, but the solutions are different: - Visual Studio: The whole folded area is selected when you click the margin - Sublime Text: When you drag down, it expands the selection from first line to the whole folded area. If you keep dragging, it will expand the selection to include next line. **Workaround**: Click the beginning of the folded line, drag to the beginning of the next line. It works, but requires much more mouse precision than clicking/dragging in margin area. **Suggestion**: A simple question: how often do you want to select **only** the first line when you click the margin of **folded** area? I believe it's very rare, so Visual Studio's solution is desired. VS Code version: Code 1.27.2 (f46c4c469d6e6d8c46f268d1553c5dc4b475840f, 2018-09-12T16:17:45.060Z) OS version: Windows_NT x64 10.0.17134 <details> <summary>System Info</summary> |Item|Value| |---|---| |CPUs|Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz (8 x 3096)| |GPU Status|2d_canvas: enabled<br>checker_imaging: disabled_off<br>flash_3d: enabled<br>flash_stage3d: enabled<br>flash_stage3d_baseline: enabled<br>gpu_compositing: enabled<br>multiple_raster_threads: enabled_on<br>native_gpu_memory_buffers: disabled_software<br>rasterization: enabled<br>video_decode: enabled<br>video_encode: enabled<br>webgl: enabled<br>webgl2: unavailable_off| |Memory (System)|15.85GB (4.97GB free)| |Process Argv|C:\Program Files\Microsoft VS Code\Code.exe D:\Repos\modern\NovaApi| |Screen Reader|no| |VM|0%| </details> <!-- generated by issue reporter -->