These are the the ones where we already had a Register object being
used. Some places are still using unsigned which I did not convert.

This iteration drops hunks where the loop body adds more elements.

This reverts commit 3614f65a7ba9d925010e3316a1d93bcebc632178.

fixupImmediateBr seems to resize ImmBranches.

- Add `MachineBlockFrequencyAnalysis`.
- Add `MachineBlockFrequencyPrinterPass`.
- Use `MachineBlockFrequencyInfoWrapperPass` in legacy pass manager.
- `LazyMachineBlockFrequencyInfo::print` is empty, drop it due to new
pass manager migration.

- Add `LiveIntervalsAnalysis`.
- Add `LiveIntervalsPrinterPass`.
- Use `LiveIntervalsWrapperPass` in legacy pass manager.
- Use `std::unique_ptr` instead of raw pointer for `LICalc`, so
destructor and default move constructor can handle it correctly.

This would be the last analysis required by `PHIElimination`.

`ArrayRef` is supposed to be passed by value:

https://github.com/llvm/llvm-project/blob/bda05140fb758156ae35f3919e6283d94bfa3905/llvm/include/llvm/ADT/ArrayRef.h#L38-L39

The comment already succnictly explains the relevant parts of the radar.

After register coalescing, some `DBG_VALUE`s can have incorrect info.
For example, if a `DBG_VALUE` has a register operand `%0`, but it
resides in a live range of `%1`, it has incorrect info after `%0` and
`%1` are coalesced. See the comments for more details.

This does not have meaningful changes on our variable debug info
coverage or compilation time, which is good news.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D151125