This removes the old legacy PM "intervals" analysis pass (aka
IntervalPartition). It also removes the associated Interval and
IntervalIterator help classes.
Reasons for removal:
1) The pass is not used by llvm-project (not even being tested by
any regression tests).
2) Pass has not been ported to new pass manager, which at least
indicates that it isn't used by the middle-end.
3) ASan reports heap-use-after-free on
++I; // After the first one...
even if false is passed to intervals_begin. Not sure if that is
a false positive, but it makes the code a bit less trustworthy.
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