zephyr: bump Zephyr version to 3.6

[davidschneider-cpi]

Zephyr 3.6 has EOL 2024-11-29 (1)

Zephyr 3.2 deprecated several macros and include files which makes it hard to maintain compatibility between newer versions and 3.1.

• FLASH_AREA_ macros are deprecated (zephyrproject-rtos/zephyr@54db76b)
• including <zephyr/zephyr.h> is deprecated (zephyrproject-rtos/zephyr@7f2ad2e)

Fix various warnings:

• initialization of struct spi_config
• unused function lfs2_mlist_isopen

Run CI build job with CONFIG_WARNINGS_AS_ERRORS enabled. This configuration option is available since Zephyr 3.5.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.39%. Comparing base (fa23e4b) to head (b20c0c4).

❗ Current head b20c0c4 differs from pull request most recent head be8ca73. Consider uploading reports for the commit be8ca73 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #14471   +/-   ##
=======================================
  Coverage   98.39%   98.39%           
=======================================
  Files         161      161           
  Lines       21204    21204           
=======================================
  Hits        20864    20864           
  Misses        340      340           

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[github-actions]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS

[MaureenHelm]

See #9335

[davidschneider-cpi]

I'm closing this attempt in favour of the other ongoing requests to move to a recent version of Zephyr.

If zephyrproject-rtos/zephyr#71912 gets accepted, the whole discussion about user friendly device names could get resolved.