[clang-tools-extra] clangd: Extend index references with constructor calls through forwarding (PR #169742)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Linux-->
# :penguin: Linux x64 Test Results

* 3053 tests passed
* 7 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### Clangd Unit Tests
<details>
<summary>Clangd Unit Tests._/ClangdTests/FindReferences/ForwardingInIndex</summary>

```
Script:
--
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/tools/clang/tools/extra/clangd/unittests/./ClangdTests --gtest_filter=FindReferences.ForwardingInIndex
--
/home/gha/actions-runner/_work/llvm-project/llvm-project/clang-tools-extra/clangd/unittests/XRefsTests.cpp:2744
Value of: findReferences(AST, Header.point(), 0, Index.get(), true) .References
Expected: has 2 elements where
element #0 range is (R: 8:6-8:10),
element #1 range is (R: 3:20-3:31)
  Actual: { 8:6-8:10 at file:///clangd-test/header.hpp (container: Test) [decl] [def] }, which has 1 element


```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/169742