Add kernel parameter support for dm-verity options

[aale24]

Implement rd.kiwi.verity_options= parameter to allow runtime customization of veritysetup options

Fixes #2837 .

Changes proposed in this pull request:

Add kernel command line parsing to kiwi-veritytab-setup.sh. The script already sources dracut-lib.sh, which provides access to getarg function.

Supported Options:

panic-on-corruption - System panics on corruption detection
restart-on-corruption - System restarts on corruption (default)
ignore-corruption - Ignore corruption (debugging only)
ignore-zero-blocks - Ignore zero blocks
check-at-most-once - Verify blocks only once
Veritysetup options as documented in veritysetup(8)

Usage Example:

rd.kiwi.verity_options=panic-on-corruption,check-at-most-once

Adding rd.kiwi.verity_options=panic-on-corruption

[63.380164] dracut-initqueue[893]: ///lib/dracut/hooks/initqueue/settled/71-kiwi-veritytab-setup.sh@50(): veritysetup open /dev/disk/by-uuid/**** verityroot /dev/disk/by-uuid/**** **** --hash-offset=**** --hash-block-size=4096 --panic-on-corruption

[schaefi]

Looks great 👍 Thanks much