[clang-tools-extra] [clang-doc] place HTML/JSON output inside their own directories (PR #150655)

[Erick Velez via cfe-commits]

evelez7 wrote:

> Is the plan just to handle this for JSON and Mustache for now, and when we have templates for Markdown (and whatever else) they'll just use this pattern? And I guess migrate any tests we want to keep for HTML once we switch to the mustache implementation by default?

That sounds like a good plan. Migrating any HTML tests would also serve as good regression testing since the basic test was matched to whatever Clang-Doc's output was at the time.

https://github.com/llvm/llvm-project/pull/150655