[Support] Add format object for interleaved ranges (#135517)

Add two new format functions for printing ranges: `interleaved` and
`interleaved_array`.

This is meant to improve the ergonomics of printing ranges. Before this
patch, we have to either use `llvm::interleave` or write a for loop by
hand. For example:

Before:
```c++
ArrayRef<Type> types = ...;
ArrayRef<Values> values = ...;
LLVM_DEBUG({
  llvm::dbgs() << "Types: ";
  llvm::interleave_comma(llvm::dbgs(), types);
  llvm::dbgs() << "\n";
  llvm::dbgs() << "Values: [";
  llvm::interleave_comma(llvm::dbgs(), values);
  llvm::dbgs() << "]\n";
}):
```

After:
```c++
ArrayRef<Type> types = ...;
ArrayRef<Values> values = ...;
LLVM_DEBUG(llvm::dbgs() << "Types: " << interleaved(types) << "\n");
LLVM_DEBUG(llvm::dbgs() << "Values: " << interleaved_array(values) << "\n");
```

The separator and the prefix/suffix strings are customizable.

0 files changed, 0 insertions, 0 deletions