Fix query for GR_GL_IMPLEMENTATION_COLOR_READ_FORMAT for GrPixelConfigs that aren...

Fix query for GR_GL_IMPLEMENTATION_COLOR_READ_FORMAT for GrPixelConfigs that aren't renderable

We recently separated renderabibilty by Skia from FBO-bindable ( https://skia-review.googlesource.com/4345). Overlooked in that change was the necessity to be able to query GR_GL_IMPLEMENTATION_COLOR_READ_FORMAT and _TYPE for formats that we don't support rendering to Skia but are legal color attachment formats.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2489643002

Review-Url: https://codereview.chromium.org/2489643002