Use signatures in most of backend/ and consoles/ as possible

[okurz]

No description provided.

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching backend/**.pm:

• Consider running manual verification tests, especially for non-qemu backends

Files matching consoles/**.pm:

• Consider running manual verification tests on real hardware, especially for non-qemu backends

This is an automatically generated QA checklist based on modified files

[codecov]

Codecov Report

Merging #1986 (d0a739e) into master (1f2717e) will increase coverage by 0.04%.
The diff coverage is 94.11%.

@@            Coverage Diff             @@
##           master    #1986      +/-   ##
==========================================
+ Coverage   77.56%   77.60%   +0.04%     
==========================================
  Files          70       70              
  Lines        7274     7280       +6     
==========================================
+ Hits         5642     5650       +8     
+ Misses       1632     1630       -2     

Impacted Files	Coverage Δ
consoles/sshIucvconn.pm	27.27% <0.00%> (-1.30%)	⬇️
backend/console_proxy.pm	95.00% <100.00%> (-0.24%)	⬇️
backend/qemu.pm	58.94% <100.00%> (ø)
consoles/VNC.pm	60.42% <100.00%> (+0.32%)	⬆️
consoles/amtSol.pm	14.28% <100.00%> (+1.55%)	⬆️
consoles/console.pm	91.89% <100.00%> (+0.46%)	⬆️
consoles/network_console.pm	100.00% <100.00%> (ø)
consoles/serial_screen.pm	100.00% <100.00%> (ø)
consoles/sshVirtshSUT.pm	50.00% <100.00%> (+8.33%)	⬆️

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