Packaging Update

• d/salsa-ci.yml: add standard salsa-ci configuration
• d/gbp.conf: cleanup and set pigeonhole as global component
• d/watch: bundle pigeonhole source
• d/rules: remove phony declarations
• d/control: add ${misc:Pre-Depends} to dovecot-core
• d/control: use https url
• d/control: add explicit Rules-Requires-Root: binary-targets
• d/rules: configure with --with-rundir=/run/dovecot

After these changes, the new upstream version 2.3.10.0 can be simply imported with gbp import-orig --uscan

p.s.: sample ci-run: https://salsa.debian.org/cgzones/dovecot/pipelines/138199