Because we can't expand generator expressions for the lit tests,This patch restructures part of LLDB's testing configuration:
1. I moved the test dependencies up the chain so every dotest dependency becomes a lit dependency as well. It wouldn't make sense for dotest to have other dependencies when it's being run by lit. Lit on the other hand can still specify extra dependencies.
2. I replaced as much generator expressions with variables as possible. This is consistent with the rest of LLVM and doesn't break generators that support multiple targets (MSVC, Xcode). This wasn't a problem before, but now we need to expand the dotest arguments in the lit configuration and there's only one test suite even with multiple targets.
3. we need to set the path to the debugserver in the `_STR` variable so it's expanded properly without breaking multi-target generators such as MSVC and XcodeI moved lldb-dotest into it's own directory under utils since there's no need anymore for it to located under `test/`.