Revamp default from_scm(scm, fallback)

It is now optional to define from_scm(scm, fallback) in specializations of scm_conversions. When it is undefined, robust_scm_conversions provides a default implementation.

This also eliminates overloading of ::from_scm(scm, fallback).

Anyone who chooses to review by commit may wish to peek at the final commit first, since it removes some stopgap code added in an earlier commit. I'm sorry for the churn, but it's probably better this way than as one big change.

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Very nice! I admit that I don't really understand what you are doing, but it looks consistent

One thing I noted is that you no longer use inline. Do you think this hasn't a relevance today? Or doesn't it work with the template mechanism?

https://lilypond.gitlab.io/-/lilypond/-/jobs/7809177907/artifacts/test-results/index.html

no differences

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added 9 commits

• 013abd89...73eee3a4 - 4 commits from branch lilypond:master
• ed4529b1 - Fix initialization warning
• e91abc3e - Remove unnecessary explicit template argument
• d1b28514 - Revamp default from_scm(scm, fallback)
• 7e7ee9df - more use of scm_conversions
• 592debc9 - Remove naive_robust_from_scm()

Compare with previous version

Failed to get diff for commits 013abd89 and 592debc9, resetting patch status.

added Patchnew label and removed Patchcountdown label

Failed to get diff for commits 013abd89 and 592debc9, resetting patch status.

@hahnjo, do you have any diagnostic info on the bot? All I did was rebase, and I'm having no trouble diffing these two versions myself.

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merged

changed milestone to %2.25.20

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