main/fbobject: throw invalid operation when get_attachment fails if needed

main/fbobject: throw invalid operation when get_attachment fails if needed

In most cases, if a call to get_attachment fails is because attachment
is a INVALID_ENUM. But for some specific cases, if COLOR_ATTACHMENTm
(where m >= MAX_COLOR_ATTACHMENTS) is used, it should raise an
INVALID_OPERATION exception instead.

Fixes:
GL45-CTS.direct_state_access.framebuffers_get_attachment_parameter_errors
GL45-CTS.direct_state_access.framebuffers_renderbuffer_attachment_errors

v2: extra new line before quote block. Include "color attachment" on both
    new message errors (Nicolai).

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>