Make FREEZER_CUTOFF_OOMADJ configurable

Making the freezer cutoff configurable for easier prototyping
and development. This should result in no change in behavior of
the freezer unless the device configuration is changed.

Test: Manually using device-config shell commands
Flag: EXEMPT bugfix

Bug: 370798593
Change-Id: Ibcfa6ebd6eedb617a4f632d5496671f60b8eaffb