Port more features from `please.sh sync` to git-sdk-arm64's `sync` workflow

[dscho]

The git-sdk-32 and git-sdk-64 repositories are kept up to date by a scheduled sync workflow that essentially runs the please.sh sync command from git-for-windows/build-extra.

Due to its heritage, please.sh does not really run well in the CI, and it showed when we tried to port the sync workflow over to git-sdk-arm64 while keeping it on hosted runners (i.e. not ARM64 runners). Therefore, we could not use anything from the please.sh script and rewrote the functionality in PowerShell.

This rewrite is not yet complete, it still needs:

• the same pacnew handling (done here),
• the asciidoctor handling (done here),
• and while at it we need to implement something new: special-case etc/pacman.conf by carrying over the IgnorePkg changes (done here).

Then we will want to port those changes over to the

• i686 and the
• x86_64 SDKs, and then
• remove the sync command from please.sh.

Originally posted by @dscho in #4197 (comment)