Rename the internal cppgc directory to src/heap/cppgc-internal/ to clearly distinguish it from the public include/cppgc/ headers and avoid potential naming confusion. The collision occurs on Windows builds where -Wmicrosoft-include is enabled by Clang in MSVC compatible mode. MSVC on Windows uses different order of directories where the files are searched by the compiler and `#include "cppgc/blah.h"` in public headers might end up including "src/heap/cppgc/blah.h" if it exists. All internal #include paths, include guards, and build configurations (BUILD.gn and BUILD.bazel) have been updated to reflect the new path. TAG=agy CONV=47b06028-d652-41a8-b4f1-39e3cc478096 Bug: 515252150 Change-Id: Idf7ca1d193a8b6bb9d53b22f01320f4363df36f4 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/7963663 Commit-Queue: Igor Sheludko <ishell@chromium.org> Reviewed-by: Michael Lippautz <mlippautz@chromium.org> Auto-Submit: Igor Sheludko <ishell@chromium.org> Commit-Queue: Michael Lippautz <mlippautz@chromium.org> SLSA-Policy-Verified: SLSA Policy Verification Service <devtools-gerritcodereview-exitgate@google.com> Cr-Commit-Position: refs/heads/main@{#108143}