[BPF] fix a use after free bug
Commit fff2721286e1 ("[BPF] Fix CO-RE bugs with bitfields")
fixed CO-RE handling bitfield issues. But the implementation
introduced a use after free bug. The "Base" of the intrinsic
might be freed so later on accessing the Type of "Base"
might access the freed memory. The failed test case,
is exactly used to test such a case.
Similarly to previous attempt to remember Metadata etc,
remember "Base" pointee Alignment in advance to avoid
such use after free bug.