net/wifi-firmware-*kmod: improve build logic, add flavors, update fw version

• update framework to no longer depend on local distfiles for firmware(9) but generate the Makefile hierarchy in post-extract. Keep a Makefile.inc.in in files for simplicity.
• update extracting WHENCE parts using a local WHENCE.awk.in in files and a pattern to match the section(s).
• use the already prepared FWSUBS sections for flavors and add the FWDRV as "default". Generate the CONFLICTS_INSTALL conflict and PKGNAMESUFFIX entries. Adjust paths and logic for flavors. Depend on the flavors rather the combined ("default flavor") packages by default if someone installs wifi-firmware-kmod. The wifi-firmware-${name}-kmod packages are still built for older versions of fwget shipping in releases.
• add support for iwlwifi and ath12k firmware
• update firmware to linux-firmware.git tag: 20240513 for all drivers.

Sponsored by: The FreeBSD Foundation
Reviewed by: jrm
Differential Revision: https://reviews.freebsd.org/D44945