glsl: Add operator for .length() method on implicitly-sized arrays

glsl: Add operator for .length() method on implicitly-sized arrays

ARB_shader_storage_buffer_object extension (promoted to core in 4.3) allows us
to call .length() method on arrays declared without an explicit size. The length is
determined at link time as a maximum array access.

Fixes: 273f61a0051a ("glsl: Add parser/compiler support for unsized array's length()")
Signed-off-by: Yevhenii Kolesnikov <yevhenii.kolesnikov@globallogic.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11952>