Script for move-to-framework with history

[mpg]

As pointed out by Gilles, the script for moving files to the framework repo while preserving their history is going to be an essential maintainer tool for the next few month, so it would make sense to make it more robust and easy to use (and possibly have it in the framework repo).

[davidhorstmann-arm]

Estimating < 1 ideal day, around 3 actual days for this, so adding size-s

[mpg]

Github doesn't let me properly link the PR, but this is Mbed-TLS/mbedtls-docs#145

For the record, the script as it stands has been used successfully a number of times, so there was a consensus on merging that PR quickly, and addressing any leftover comments in a follow-up - it makes little sense to keep the PR unmerged while we're already actively using the script.

@bensze01 I think you said you'd review it?

[gilles-peskine-arm]

@mpg I believe Harry was going to use the script to rewrite #114. @Harry-Ramsey, if you use the script from Mbed-TLS/mbedtls-docs#145 and you're ok with it, would you mind approving Mbed-TLS/mbedtls-docs#145 ? In the mbedtls-docs repository, the standard for approving is “meets basic expectations, not harmful”, a lot weaker than in our other repositories. So if you've successfully used the script, that's probably good enough for approving.

(I earlier requested changes on Mbed-TLS/mbedtls-docs#145 because the version at the time didn't work for me. David has since then fixed the problem I ran into, but I haven't had a chance to use the new version, so I dismissed my earlier review but I don't feel comfortable approving the new version.)