[lldb] Add array decaying (#210918)
In C, an array name in an expression "decays" into a pointer to its
first element. LLDB did not honor this: commands like `memory read
my_array` did not work correctly, because an aggregate type has no
scalar value, so trying to obtain one (ResolveValue/GetValueAsUnsigned)
failed.
This MR adds explicit array decay: for array-typed expressions, the
address of the array object itself is used instead of its (non-existent)
scalar value.
