d/pcscd.init: restore, with simplifications and aligning with systemd unit

Dear pcscd maintainer,

Would you please consider restoring the init script for pcscd?

Currently for anyone using a supervision system other than systemd, pcscd installations are broken for new users by a5761b8b in pcscd/2.2.0-1 and for upgrades by 00c98af7 in the latest version, pcscd/2.3.0-3. It could be unpleasant for stable users upgrading to trixie as there is no indication that this is going to break for them so they may have no idea why functions no longer work - applications like Yubico Authenticator just silently do nothing.

With this merge request I have added some commits that simplify the previous version of the init script, removing 20-odd lines, to reduce the carrying cost of this script, in case that was a concern.

The script is also updated to use the same environment variable as the systemd service file (although this one fell through the cracks, changes like environment variable usage are a good reason to keep all service files together with the relevant service so there is no dislocation of package versioning across changes). These commits might be ripe for squashing if you wish but I kept the changes separate for now for clarity.

I have tested this change successfully. This is a combination of software I will continue using so would be able to help spot future regressions.

Many thanks,

Andrew

(Closes: #1090333)