[Linux] Lock CHIP stack before calling WiFi diagnostic delegate (proj…

…ect-chip#32137)

* Get rid of static functions by wrapping glib callbacks with lambda

* Get rid of the rest of static functions

* Keep sWiFiIfName as an instance member

* Lock CHIP stack before calling WiFi diagnostic delegate

* Do not use sInstance internally in ConnectivityManagerImpl

* Fix signatures for properties-changed and scan-done callbacks

* Keep all members of ConnectivityManagerImpl as instance members

* Fix freeing char objects allocated by glib

* Restyled by clang-format

* Fix compilation warnings

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Co-authored-by: Restyled.io <[email protected]>