This patch addresses the issue #129543.
After this patch DWARFExpression does not call DWARFUnit directly and does not depend on
lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp and a lot of clang code.
After this patch the size of lldb-server binary (Linux Aarch64) is reduced from 47MB to 17MB.