Support transition to new non-free-firmware component

APT doesn't care all that much about components and this MR actually makes this a tiny bit more true.

The main feature through is introducing notices for users who have likely missed reading the release notes (which have yet to actually include a section about this).

The generated messages are: a) for a user who has non-free but not non-free-firmware in its sources.list:

N: Repository 'Debian bookworm' changed its 'non-free component' value from 'non-free' to 'non-free non-free-firmware'
N: More information about this can be found online in the Release notes at: https://www.debian.org/releases/bookworm/amd64/release-notes/ch-information.html#non-free-split

and b) for a user who has no non-free, but has a (hardcoded) firmware package installed and not downloadable which is shipped in non-free-firmware:

N: Repository 'Debian bookworm' changed its 'firmware component' value from 'non-free' to 'non-free-firmware'
N: More information about this can be found online in the Release notes at: https://www.debian.org/releases/bookworm/amd64/release-notes/ch-information.html#non-free-split

If you think the first line in each sounds a bit cryptic: That is right, but

• I am reusing an existing message here as I don't want to annoy translators with two new strings for messages which in an ideal world nobody ever sees and reads (although if the last release is any indication…)
• I have a hard time coming up with a better message which fits in one line and wouldn't be confusing anyhow as it is technically a layer violation
• All that message really should do is get people to read the release notes – more cryptic = better 😜

Compared to the draft version:

• slightly refactored the code to avoid code duplicates, but no practical change
• the link chosen based on release-notes discussion
• I picked component instead of section in the first line as somehow that is what the release-notes seem to use (for now) in the chapter I link to.
• list of firmware packages to suggest adding non-free-firmware for (scenario b) guesstimated based on mails & bugreport plans and current repo content

crude shell script to generate firmware package list

```sh #!/bin/sh set -e OLD_REL='bullseye' NEW_REL='bookworm' MIRROR='https://deb.debian.org/debian' APTHELPER=/usr/lib/apt/apt-helper

download_packages_file() { "APTHELPER" download-file "{MIRROR}/dists/{1}/{2}/binary-{3}/Packages.xz" "Packages_{1}${2}${3}.xz" } download_all_packages_files() { "APTHELPER" download-file "{MIRROR}/dists/{1}/Release" "Release-{1}" for ARCH in (grep '^Architectures: ' "Release-{1}" | cut -d':' -f 2 | tr ' ' '\n'); do if [ -z "ARCH" -o "ARCH" = 'all' ]; then continue; fi download_packages_file "$1" "2" "ARCH" done }

download_all_packages_files "$NEW_REL" 'non-free-firmware' download_all_packages_files "$OLD_REL" 'non-free'

get_binary_firmware_package_names() { "APTHELPER" cat-file Packages_{NEW_REL}non-free-firmware*.xz | grep '^Package: ' | cut -d' ' -f 2

    # https://lists.debian.org/debian-boot/2023/01/msg00235.html
    for SRCPKG in 'amd64-microcode' 'intel-microcode' \
            'atmel-firmware' 'firmware-ast' 'firmware-sof' 'rtl8723bt-firmware' \
            'bluez-firmware' 'dahdi-firmware' 'firmware-nonfree' \
            'zd1211-firmware' \
            'ixp4xx-microcode' \
            'midisport-firmware' \
    ; do
            apt-helper cat-file Packages_${OLD_REL}_non-free_*.xz | grep-dctrl -nS -s Package "$SRCPKG"
    done

}

ixp4xx-microcode: #1029814

get_binary_firmware_package_names | sort -u |
sed -e '/^ixp4xx-microcode$/ d' |
sed -e 's#^(.*)$#"\1",#' | tr '\n' ' '

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