Gdsfactory

- containers use `gf.functions.copy_settings` instead of trying to detect `component=` from kwargs
- `Port._copy()` is now `Port.copy()`
- bend_euler `p=0.5` as default based on this [paper](https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-25-8-9150&id=362937)
- rectangle has 4 ports by default (similar to compass), it just includes the `centered` parameter
- gf.grid accept component factories as well as components and is a cell

- fix cutback_component bend
- add `gf.routing.route_quad`

- add `gdsfactory.to_3d.to_stl`

- adjust z position for lumerical simulation region as well as port locations
- `Component.show()` and `Component.plot()` do not clear_cache by default (`clear_cache=False`)

- write_sparameters in lumerical writes simulation_settings in YAML
- replace port_width with port_margin in simulation_settings
- rename `Component.get_porst_east_west_spacing` as `Component.get_ports_ysize()`
- add `Component.get_ports_ysize()`
- fix `mzi` `with_splitter`
- enable `vars` variables in component_from_yaml
- gdsdiff accepts test_name, and uses the path of the test_file for storing GDS files
- add functools cache decorator for gdsfactory.import_gds and gdsfactory.read.gds
- rename cache with lru_cache(maxsize=None) to keep compatibility with python3.7 and 3.8
- update to phidl==1.6.0 and gdspy==1.6.9 in requirements.txt
- new gf.path.extrude adapted from phidl

- rename `component_from` to `read`
- remove `gf.bias`
- remove `gf.filecache`
- add `get_layer_to_sidewall_angle` in layer_stack
- rename `gf.lys` to `gf.layers.LAYER_COLORS` to be consistent