[//gpu] Eliminate GLES2 command decoders' lazy binding code on Windows

The command decoders' lazy binding is a no-op if the following is true:
- For the validating command decoder, Texture::HasUnboundLevelImage() is
  false
- For the passthrough command decoder,
  TexturePassthrough::is_bind_pending() is false

Following recent refactorings and simplifications, neither Texture::SetUnboundLevelImage() nor TexturePassthrough::set_bind_pending() is
ever called on Windows, meaning that the decoders' lazy binding is
always a no-op on that platform. This CL eliminates that code from being
built on Windows, leaving Apple as the only remaining platform with lazy
binding (will be tackled once the VTVDA refactoring is complete).

Bug: 1323341
Change-Id: I343294a4fa5cbb0d0e953092df20b2a0264b9312
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4594402
Commit-Queue: Colin Blundell <blundell@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1154856}