Reverts a4cc033408fe0a69aad6865ddc7e020d64098f20.
Relanding the original patch as-is, but changing the `__builtin_debugtrap`s to explicitly set breakpoints. Some bots failed to compile the tests when `__builtin_debugtrap` was used.
Also adding `REQUIRES: lldb-formats-compatibility` to the test because some build-bots run the tests with an LLDB version that doesn't support the `FindDirectNestedType` API.
Original commit message:
This patch revives the llvm::PointerIntPair LLDB data-formatter. The previous version was commented out because it relied on expression evaluation and was hence slow/brittle. The formatter in this PR doesn't rely on evaluating expressions.
Drive-by change:
* removes the llvm::PointerUnion formatter which was also commented out. A future version of it will look very different than it does now, so there's no point in keeping it because the diff won't be helpful in a review.
0b9d07860a