ubx: Refactor codebase in order to improve usability

During testing and code inspection, there were various anti-patterns
on this (and U-Blox driver) codebase(s), including obfuscation, and
lack of data validation. This made it increasingly difficult to
introduce further variants of u-blox GNSS modems.

With this patch, both the UBX modem and the M8 driver have been
refactored to ease the reliability and maintainability of these
codebases. Here are some highlights:

WRT UBX modem:
- Helper macros to easily create UBX frames, (including checksum
calculation), at compile time; thus, making it easier to extend UBX
commands.
- Logic validation by the inclusion of the modem_ubx testsuite, used to
refactor the code through TDD.
- Ability to receive unsolicited messages, in order to enable U-Blox
drivers to rely on modem_ubx to transceive all commands, and avoid
hopping between modem_ubx and modem_chat.

WRT M8 driver:
- Remove GNSS specific protocol header files. Instead, unify them under
modem/ubx/protocol.h. Background: After a survey and looking at ubxlib
SDK I conclude the UBX protocol is by definition a GNSS protocol (there
are non-GNSS u-blox modems, but they're not interfaced through UBX
protocol).
- Establish pattern to create and send/receive commands using new
foundations on modem ubx.
- Remove dependency of Modem chat, and instead use UBX unsolicited
messages to get Navigation and Satellites data.
- Switch from the auto-baudrate detection pattern to a pattern of
transitioning between an initial known baudrate to a desired baudrate,
in order to improve initialization time.
- Add dts property to configure default fix-rate.

Signed-off-by: Luis Ubieda <[email protected]>

Author: ubieda

drivers/gnss/CMakeLists.txt

@@ -11,5 +11,4 @@ zephyr_library_sources_ifdef(CONFIG_GNSS_NMEA0183_MATCH gnss_nmea0183_match.c)
 zephyr_library_sources_ifdef(CONFIG_GNSS_NMEA_GENERIC gnss_nmea_generic.c)
 zephyr_library_sources_ifdef(CONFIG_GNSS_QUECTEL_LCX6G gnss_quectel_lcx6g.c)
 zephyr_library_sources_ifdef(CONFIG_GNSS_U_BLOX_M8 gnss_u_blox_m8.c)
-zephyr_library_sources_ifdef(CONFIG_GNSS_U_BLOX_PROTOCOL gnss_u_blox_protocol/gnss_u_blox_protocol.c)
 zephyr_library_sources_ifdef(CONFIG_GNSS_LUATOS_AIR530Z gnss_luatos_air530z.c)