[lldb][Test] Add C++ tests for DumpValueObjectOptions and enums (#93158)

DumpValueObjectOptions can only be created and modified from C++. This
means it's currently only testable from Python by calling some command
that happens to use one, and even so, you can't pick which options get
chosen.

So we have decent coverage for the major options that way, but I want to
add more niche options that will be harder to test from Python (register
field options).

So this change adds some "unit tests", though it's stretching the
definition to the point it's more "test written in C++". So we can test
future options in isolation.

Since I want to add options specific to enums, that's all it covers.
There is a test class that sets up the type system so it will be easy to
test other types in future (e.g. structs, which register fields also
use).