Cleaner artifact generation

[etpinard]

inspired by https://github.com/sglyon/PlotlyBase.jl/blob/master/deps/generate_artifacts.jl so that we now use the following official methods exported from Pkg.Artifacts:

• create_artifacts
• archive_artifact (which creates a new tarball and should work across platforms, unlike tar)
• bind_artifact! (which writes the Artifact.toml content)

Moreover, I think we'll be able to remove

dash-textarea-autocomplete/.github/workflows/tests.yml

Lines 43 to 52 in 8731437

	- name: Set-up DastTextareaAutocomplete artifact directory
	# This step is used to skip artifact download as the url/hash found
	# in 'Artifacts.toml' might not be valid anymore after `npm run build`
	run: |
	julia -e 'using Pkg.Artifacts; \
	using Tar, TOML; \
	res_key = "dash_textarea_autocomplete_resources"; \
	d = TOML.tryparsefile("Artifacts.toml"); \
	hash = d[res_key]["git-tree-sha1"]; \
	Tar.extract("deps/deps.tar", mkpath(artifact_path(Base.SHA1(hash))));'

that is, Pkg.add(url=\"$GITHUB_SERVER_URL/$GITHUB_REPOSITORY\", rev=\"$GITHUB_SHA\"); should just work now.

---

Oh well, we don't need to merge this PR and maybe we shouldn't for now.

@Felix-Gauthier I think we have spent enough time on dash-textarea-autocomplete in the last 10 days or so. Consider this PR documentation for future dash-textarea-autocomplete work.

[Felix-Gauthier]

This looks great, we're better of using this one julia script than postbuild.sh + tweaks to CI

We could do a patch release after the holidays to use it 🚀