docs: read (complex) defaults from implementation signature

[ST-DDT]

This PR allows displaying potentially complex (expressions, options, arrays) default values in the docs.

Here an example with a fictional expression default value.

Here is an example from the actual docs:

Old

New

Diff

[codecov]

Codecov Report

Merging #656 (57f481c) into main (e643835) will not change coverage.
The diff coverage is n/a.

❗ Current head 57f481c differs from pull request most recent head 94828e0. Consider uploading reports for the commit 94828e0 to get more accurate results

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