[onert-micro] Fix 3 critcal and 5 major svace defects

[chunseoklee]

Let's fix svace defects on the latest master. It seems to be caused by recent kernel update.

defect list link

N	Severity	ID	Classification	Checker	File Path
1	Critical	12230	Undecided	BUFFER_OVERFLOW.PROC	/tmp/source_root/ONE/onert-micro/luci-interpreter/src/kernels/Mean.cpp:101
2	Critical	12231	Undecided	BUFFER_OVERFLOW.PROC	/tmp/source_root/ONE/onert-micro/luci-interpreter/src/kernels/Mean.cpp:101
3	Critical	12234	Undecided	DIVISION_BY_ZERO	/tmp/source_root/ONE/onert-micro/luci-interpreter/pal/common/PALL2Pool2D.h:69
4	Major	12210	Undecided	DEREF_OF_NULL.RET.STAT	/tmp/source_root/ONE/onert-micro/luci-interpreter/src/kernels/Slice.cpp:89
5	Major	12211	Undecided	DEREF_OF_NULL.RET.STAT	/tmp/source_root/ONE/onert-micro/luci-interpreter/src/kernels/PadCommon.cpp:131
6	Major	12232	Undecided	DEREF_OF_NULL.RET.STAT	/tmp/source_root/ONE/onert-micro/luci-interpreter/src/kernels/Conv2D.cpp:294
7	Major	12233	Undecided	DEREF_OF_NULL.RET.STAT	/tmp/source_root/ONE/onert-micro/luci-interpreter/src/loader/GraphLoader.cpp:113
8	Major	12235	Undecided	SIGNED_TO_BIGGER_UNSIGNED	/tmp/source_root/ONE/onert-micro/luci-interpreter/pal/common/PALMean.h:148

[chunseoklee]

cc @BalyshevArtem @SlavikMIPT

[chunseoklee]

ahub analysis with patch which try to resolve 3 critical defects