Port XMM signal interface from paul/infineon branch
Fix some modem signal polling cleanup issues and Add signal interface for XMM modems via +XCESQ command (this adds SNR / RSSNR values for when connected via LTE).
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Fix some modem signal polling cleanup issues and Add signal interface for XMM modems via +XCESQ command (this adds SNR / RSSNR values for when connected via LTE).