patch: change fuzz setting default from 2 to a safer 0

[xnox]

Patches can be incorrectly applied (duplicated patching), or no longer
have correct meaning, if they are applied with fuzz.

To prevent such conditions from happening, change the fuzz setting
default to a safer value of 0.

This also matches the behaviour of dpkg [1].

This will cause some packages to fail to build, the mitigation strategies are:

• rebase and regenerate patches with clean and up to date context

• add "with: fuzz: 2" argument to the patches pipeline

[1] https://salsa.debian.org/dpkg-team/dpkg/-/blob/main/scripts/Dpkg/Source/Quilt.pm?ref_type=heads#L188

To land this safely:

• search world rebuild logs for fuzz application
• or locally test rebuild all patch applications
• mark up the ones that are fuzzy with fuzz 2
• roll out this update
• work to burn down all users of fuzzy 2, down to 0
• consider removing fuzzy argument from the pipeline all together
• scope is approximately 395 melange files
• one can test this locally by copying this pipeline into the individual packaging repositories; possibly modify it to exit 1 after patches were applied, to quickly iterate across all packages to recheck if patches are clean