Refactor renderer to support vulkan extensions

[xiaowei-guan]

#101
Main changes:

• Make FlutterTizenView SetEngine and CreateRenderSurfcae methods private.
• Add TizenRendererNui class to decorate GL renderer for NUI.
• Remove GL renderer methods from FlutterTizenView.
• Do not call CreateSurface and DestorySurface in FlutterTizenView.
• Move GetRendererConfig to renderer.
• Extract a new class for GL renderer.
• Move create texture code from texture registrar to renderer.

[JSUYA]

Hi about this commit 8121f5e ...
There was a similar case at #90.
Did you check window's code?

As the feature of tizen embedder has modified, there have been cases where we needed additional mock-up of the embedder api.
I haven't tested it yet, but if you look at flutter_windows_texture_registrar_unittests.cc in windows, you might need to add a mock-up of PostRenderThreadTask.
(flutter/engine/src/flutter/shell/platform/windows/flutter_windows_texture_registrar_unittests.cc)

[xiaowei-guan]

Hi about this commit 8121f5e ... There was a similar case at #90. Did you check window's code?

As the feature of tizen embedder has modified, there have been cases where we needed additional mock-up of the embedder api. I haven't tested it yet, but if you look at flutter_windows_texture_registrar_unittests.cc in windows, you might need to add a mock-up of PostRenderThreadTask. (flutter/engine/src/flutter/shell/platform/windows/flutter_windows_texture_registrar_unittests.cc)

Fail to run texture unittest, because texture registrar fail to create ExternalTexture. Not related to Embedder API.
I added a macro definition for this unit tests.