[LAA] Split out a helper to print a collection of memchecks

This is effectively an NFC but we can no longer print the index of the
pointer group so instead I print its address.  This still lets us
cross-check the section that list the checks against the section that
list the groups (see how I modified the test).

E.g. before we printed this:

    Run-time memory checks:
    Check 0:
      Comparing group 0:
        %arrayidxC = getelementptr inbounds i16, i16* %c, i64 %store_ind
        %arrayidxC1 = getelementptr inbounds i16, i16* %c, i64 %store_ind_inc
      Against group 1:
        %arrayidxA = getelementptr i16, i16* %a, i64 %ind
        %arrayidxA1 = getelementptr i16, i16* %a, i64 %add
    ...
    Grouped accesses:
      Group 0:
        (Low: %c High: (78 + %c))
          Member: {%c,+,4}<%for.body>
          Member: {(2 + %c),+,4}<%for.body>

Now we print this (changes are underlined):

    Run-time memory checks:
    Check 0:
      Comparing group (0x7f9c6040c320):
                       ~~~~~~~~~~~~~~
        %arrayidxC1 = getelementptr inbounds i16, i16* %c, i64 %store_ind_inc
        %arrayidxC = getelementptr inbounds i16, i16* %c, i64 %store_ind
      Against group (0x7f9c6040c358):
                     ~~~~~~~~~~~~~~
        %arrayidxA1 = getelementptr i16, i16* %a, i64 %add
        %arrayidxA = getelementptr i16, i16* %a, i64 %ind
    ...
    Grouped accesses:
      Group 0x7f9c6040c320:
            ~~~~~~~~~~~~~~
        (Low: %c High: (78 + %c))
          Member: {(2 + %c),+,4}<%for.body>
          Member: {%c,+,4}<%for.body>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243354 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/LoopAccessAnalysis.h

@@ -414,6 +414,10 @@ public:
   void print(raw_ostream &OS, unsigned Depth = 0,
              const SmallVectorImpl<int> *PtrPartition = nullptr) const;
 
+  /// Print \p Checks.
+  void printChecks(raw_ostream &OS, const SmallVectorImpl<PointerCheck> &Checks,
+                   unsigned Depth = 0) const;
+
   /// This flag indicates if we need to add the runtime check.
   bool Need;