[llvm-debuginfo-analyzer] Remove 'LVScope::Children' container.

[CarlosAlbertoEnciso]

Extracted from llvm/tools/llvm-debuginfo-analyzer/README.txt
https://reviews.llvm.org/D137933#inline-1373902

Use a chaining iterator over the other containers rather than keep a
separate container Children that mirrors their contents.

[llvmbot]

@llvm/issue-subscribers-debuginfo

Author: Carlos Alberto Enciso (CarlosAlbertoEnciso)

Extracted from [llvm/tools/llvm-debuginfo-analyzer/README.txt](https://github.com/llvm/llvm-project/blob/main/llvm/tools/llvm-debuginfo-analyzer/README.txt) https://reviews.llvm.org/D137933#inline-1373902

Use a chaining iterator over the other containers rather than keep a
separate container 'Children' that mirrors their contents.

[jalopezg-git]

@CarlosAlbertoEnciso I'll take this when I have some spare time. Thanks for making me aware of this issue,

[jalopezg-git]

@CarlosAlbertoEnciso: from LVScope.h,

  // Vector of elements (types, scopes and symbols).
  // It is the union of (*Types, *Symbols and *Scopes) to be used for
  // the following reasons:
  // - Preserve the order the logical elements are read in.
  // - To have a single container with all the logical elements, when
  //   the traversal does not require any specific element kind.
  std::unique_ptr<LVElements> Children;

and in particular

// - Preserve the order the logical elements are read in.

cannot be met if we use a chaining iterator over the other containers. Is there any particular reason why that was mentioned in the cited comment? Is that important? If not, I guess we can just remove Children and offer a view over the union of the other containers.

[llvmbot]

@llvm/issue-subscribers-debuginfo

Author: Carlos Alberto Enciso (CarlosAlbertoEnciso)

Extracted from [llvm/tools/llvm-debuginfo-analyzer/README.txt](https://github.com/llvm/llvm-project/blob/main/llvm/tools/llvm-debuginfo-analyzer/README.txt) https://reviews.llvm.org/D137933#inline-1373902

Use a chaining iterator over the other containers rather than keep a
separate container Children that mirrors their contents.

[CarlosAlbertoEnciso]

// - Preserve the order the logical elements are read in.

cannot be met if we use a chaining iterator over the other containers. Is there any particular reason why that was mentioned in the cited comment? Is that important? If not, I guess we can just remove Children and offer a view over the union of the other containers.

The idea behind the Children container is to generate a logical view where its logical elements order is very close to their programming elements from the input file. That is the default printing mode.
By using the chaining iterator, we hope to have a considerable memory reduction, which is very important.
May be we can use the LVObject::ID to recreate the original printing order via the LVSortFunction llvm::logicalview::getSortFunction().