[projmgr] Rework debugger custom properties default handling #386

Job	Run time
coverage	8m 10s
setup / config	0s
build (${{ matrix.runs_on }},${{ matrix.arch }})	0s
matrix_prep	0s
unittest (${{ matrix.runs_on }}, ${{ matrix.arch }})	0s
build-swig (${{ matrix.runs_on }}, ${{ matrix.arch }})	0s
Publish Tests Results	-1s
release	-1s
	8m 8s

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