Move the offset aligning code to stencilBlitResolveNoShaderExport
to avoid affecting color blit.

Test: dEQP-GLES3.functional.fbo.blit.default_framebuffer.*_linear_*
Bug: angleproject:5044
Change-Id: Ic2ebef94091853146424d567b0035161611ba32d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2416008
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>