[BPF] Undo transformation for LICM.cpp:hoistMinMax()

Extended BPFCheckAndAdjustIR pass with sinkMinMax() transformation
that undoes LICM hoistMinMax pass.

The undo transformation converts the following patterns:

    x < min(a, b) -> x < a && x < b
    x > min(a, b) -> x > a || x > b
    x < max(a, b) -> x < a || x < b
    x > max(a, b) -> x > a && x > b

Where 'a' or 'b' is a constant.
Also supports `sext min(...) ...` and `zext min(...) ...`.

~~~

This was previously commited as 09feee55 and reverted in
0bf9bfea because of the testbot memory leak report:
  https://lab.llvm.org/buildbot/#/builders/5/builds/34931

The memory leak issue was caused by incorrect instruction removal
sequence in skinMinMaxBB():

    I->dropAllReferences();  -------->  I->eraseFromParent();
    I->removeFromParent();   fixed to

Differential Revision: https://reviews.llvm.org/D147990