[BUG] Logging disappears for unknown reason – autostart with new (unexpected) behavior

[rexut]

Describe the bug

Logging disappears for unknown reason – currently observed on our RP2040 based boards, e.g. PicoBoy and Cytron Maker. It seems to be happen since Zephyr upstream commit 8dd9d924fe012619f465ce0375df692ed26fd4fa logging: init backend id regardless of autostart (PR zephyrproject-rtos/zephyr#84955). Before that commit we can see the following output from Shell command log status:

module_name                              | current | built-in
----------------------------------------------------------
adc_rpi                                  | inf     | inf
adc_shell                                | inf     | inf
… … …
log                                      | inf     | inf
log_mgmt                                 | inf     | inf
os                                       | inf     | inf
… … …
shell.shell_uart                         | inf     | inf
shell_uart                               | inf     | inf
soc                                      | inf     | inf
udc_rpi                                  | inf     | inf
usb_descriptor                           | err     | err
usb_device                               | err     | err
usb_transfer                             | err     | err
wdt_rpi_pico                             | inf     | inf

Since that commit we see:

module_name                              | current | built-in
----------------------------------------------------------
adc_rpi                                  | none    | inf
adc_shell                                | none    | inf
… … …
log                                      | none    | inf
log_mgmt                                 | none    | inf
os                                       | none    | inf
… … …
shell.shell_uart                         | none    | inf
shell_uart                               | none    | inf
soc                                      | none    | inf
udc_rpi                                  | none    | inf
usb_descriptor                           | none    | err
usb_device                               | none    | err
usb_transfer                             | none    | err
wdt_rpi_pico                             | none    | inf

Only log backend shell_uart_backend go bring back the normal (expected) operation.

To Reproduce
Steps to reproduce the behavior:

1. create a Bridle/Zephyr workspace from main
2. west build -b picoboy -p -d build/picoboy bridle/samples/helloshell
3. west flash -d build/picoboy

Expected behavior
Autostart logging over UART backand together with the Shell as many years before.

Impact
Shostopper: we do not know, how to come back to the old behaviour – enable/show logging at boot time – proper autostart.

Logs and console output
See above.

Screenshots
Non.

Development Environment (please complete the following information):

• OS: Linux
• Toolchain: Zephyr SDK
• Commit SHA fa6cf30

Additional context
Non.