prepare 6.3.0 release

[joamatab]

• keep python3.7 compatibility, by removing := Walrus operator
• move schematic driven flow notebook from samples to docs
• add test coverage for write_labels_gdstk

@tvt173
@Jan-David-Black

[sourcery-ai]

Sourcery Code Quality Report

❌  Merging this PR will decrease code quality in the affected files by 0.38%.

Quality metrics	Before	After	Change
Complexity	17.50 🙂	17.95 🙂	0.45 👎
Method Length	97.59 🙂	97.53 🙂	-0.06 👍
Working memory	8.87 🙂	8.82 🙂	-0.05 👍
Quality	53.19% 🙂	52.81% 🙂	-0.38% 👎

Other metrics	Before	After	Change
Lines	1685	1674	-11

Changed files	Quality Before	Quality After	Quality Change
gdsfactory/circuitviz.py	45.70% 😞	44.67% 😞	-1.03% 👎
gdsfactory/port.py	62.02% 🙂	62.02% 🙂	0.00%
gdsfactory/components/mzi_lattice.py	36.40% 😞	36.40% 😞	0.00%

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Working Memory	Quality	Recommendation
gdsfactory/circuitviz.py	viz_bk	86 ⛔	938 ⛔		0.58% ⛔	Refactor to reduce nesting. Try splitting into smaller methods
gdsfactory/components/mzi_lattice.py	mzi_lattice_mmi	6 ⭐	549 ⛔	32 ⛔	28.34% 😞	Try splitting into smaller methods. Extract out complex expressions
gdsfactory/components/mzi_lattice.py	mzi_lattice	6 ⭐	347 ⛔	18 ⛔	35.16% 😞	Try splitting into smaller methods. Extract out complex expressions
gdsfactory/port.py	map_ports_layer_to_orientation	16 🙂	170 😞	15 😞	38.18% 😞	Try splitting into smaller methods. Extract out complex expressions
gdsfactory/port.py	select_ports	11 🙂	234 ⛔	14 😞	38.92% 😞	Try splitting into smaller methods. Extract out complex expressions

Legend and Explanation

The emojis denote the absolute quality of the code:

• ⭐ excellent
• 🙂 good
• 😞 poor
• ⛔ very poor

The 👍 and 👎 indicate whether the quality has improved or gotten worse with this pull request.

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Please see our documentation here for details on how these metrics are calculated.

We are actively working on this report - lots more documentation and extra metrics to come!

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