CL: Return error code for not supported APIs The spec requires error codes to be reported for not supported API calls. Fixing to return relevant error codes. Bug: angleproject:359296611 Change-Id: Ia64bf2673446269c6557308c169f019c7dd67cc8 Signed-off-by: Gowtham Tammana <g.tammana@samsung.com> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5782397 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>