Upstream HeuristicResolver from clangd to libSema

[HighCommander4]

Filing this issue to track upstreaming the HeuristicResolver component from clangd to libSema, as originally discussed in clangd/clangd#1662.

Task list:

• Add a unit test suite for HeuristicResolver clangd/clangd#2154
• Post Discourse RFC as requested in Upstreaming HeuristicResolver to the clang libraries? clangd/clangd#1662 (comment)
• Post a PR implementing the upstreaming (draft at [clang][Sema] Upstream HeuristicResolver from clangd #121314)
• Fix bugs that depend on the upstreaming
  • Code completion not working with smart pointers in template class header files in VS Code clangd/clangd#810 (draft PR at [clang][CodeComplete] Use HeuristicResolver to resolve pointee types #121315)

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Nathan Ridge (HighCommander4)

Filing this issue to track upstreaming the HeuristicResolver component from clangd to libSema, as originally discussed in https://github.com/clangd/clangd/discussions/1662.

Task list:

• Add a unit test suite for HeuristicResolver clangd/clangd#2154
• Post Discourse RFC as requested in Upstreaming HeuristicResolver to the clang libraries? clangd/clangd#1662 (comment)
• Post a PR implementing the upstreaming

[llvmbot]

@llvm/issue-subscribers-clangd

Author: Nathan Ridge (HighCommander4)

Filing this issue to track upstreaming the HeuristicResolver component from clangd to libSema, as originally discussed in https://github.com/clangd/clangd/discussions/1662.

Task list:

• Add a unit test suite for HeuristicResolver clangd/clangd#2154
• Post Discourse RFC as requested in Upstreaming HeuristicResolver to the clang libraries? clangd/clangd#1662 (comment)
• Post a PR implementing the upstreaming