Most of this logic is similar to how we add the
`gdb-clang-incompatibility` attribute.
Some LLVM LLDB formatters will rely on LLDB features not available in
older versions of LLDB. This feature will allow those tests to add a
`REQUIRES: lldb-formatters-compatibility`, which will then mark the test
`UNSUPPORTED` for incompatible LLDB versions. I picked `19.0` pretty
arbitrarily based on when approximately the
`SBType::FindDirectNestedType` API was added to LLDB (which a future
formatter will require).
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