feat: Add scripts to output diffs of toggles and settings

[sarina]

These scripts:

• default-diff.py: Generates a report of what defaults have changed for existing flags, formatted for RST
• settings-flags-diff.py: Generates the new and removed featuretoggles & settings for this release, compared to the last release, formatted for RST. New featuretoggles & settings will also list their default values.

[sarina]

@feoh I'm moving this to draft, becaues I've found another weird thing :sigh:

[sarina]

The weirdness I found was that in Sumac, the _build/xml directory looks like this:

(8 folders)
references
|-> featuretoggles.xml

but in Teak it looks like:

(8 folders)
references
|-> featuretoggles.xml
xml
|-> references
      |-> featuretoggles.xml

Yep, two files named featuretoggles.xml and it appears only the second one is accurate. Still trying to get to the bottom of this but for now I think I've generated the files:

• https://gist.github.com/sarina/d0c7e0295b5d5e54c5bd2c1e03e2632b
• https://gist.github.com/sarina/9aa829ebb5ae947a0b9b4ee14f23e3a6

[feoh]

Thanks so much for looking into this! I'm on vacation tomorrow and will be back on Monday.

[feoh]

Amazing work. Thank you!