Maya: cleanup duplicate rendersetup code

[BigRoy]

Brief description

This resolves #2637 by removing attributes.py and pushing some of the "OpenPype" changes directly to lib_rendersetup.py.
This also refactors the single use/import of attributes.py to use this one instead.

Testing notes

Tested in Maya 2020 + 2022 using this:

Test RenderSetup absolute overrides on a camera.renderable ✅

import openpype.hosts.maya.api.lib_rendersetup as lib_rendersetup
from maya import cmds
from maya.app.renderSetup.model import (
    selector,
    renderSetup
)
    
# Make a single renderable camera
cam = cmds.createNode("camera", name="cameraMain")
cmds.setAttr(cam + ".renderable", True)

# Create a renderlayer where we set this camera to also be disabled
rs = renderSetup.instance()
disabled_layer = rs.createRenderLayer('DisabledCamera')
collection = disabled_layer.createCollection("disableRenderableCamera")
sel = collection.getSelector()
sel.setFilterType(selector.Filters.kShapes)
sel.staticSelection.set([cam])
override = collection.createOverride("renderable", "absOverride")
override.finalize("renderable")
override.setAttrValue(0)

# Create a renderlayer where we set this camera to also be enabled
rs = renderSetup.instance()
enabled_layer = rs.createRenderLayer('EnabledCamera')
collection = enabled_layer.createCollection("enableRenderableCamera")
sel = collection.getSelector()
sel.setFilterType(selector.Filters.kShapes)
sel.staticSelection.set([cam])
override = collection.createOverride("renderable", "absOverride")
override.finalize("renderable")
override.setAttrValue(1)

attr = cam + ".renderable"
assert lib_rendersetup.get_attr_in_layer(attr, layer="defaultRenderLayer") == 1
assert lib_rendersetup.get_attr_in_layer(attr, layer=disabled_layer.name()) == 0
assert lib_rendersetup.get_attr_in_layer(attr, layer=enabled_layer.name()) == 1
# change the default layer value and make sure overrides still evaluate as expected
cmds.setAttr(attr, 0)
assert lib_rendersetup.get_attr_in_layer(attr, layer="defaultRenderLayer") == 0
assert lib_rendersetup.get_attr_in_layer(attr, layer=disabled_layer.name()) == 0
assert lib_rendersetup.get_attr_in_layer(attr, layer=enabled_layer.name()) == 1

Also quickly did CreateRender in Maya 2020 to see if all Collector still collect fine. And they did! Be aware however that you'll need to add a renderable camera to the DisabledCamera layer for it to collect correctly - otherwise you'll see a no render products generated error due to the renderlayer having no renderable camera set at all.

[antirotor]

works, thanks!