[lldb][test] Fix bf16 test cases on Arm 32-bit (#161528)
Fixes #157674
On ARM, the presence of a specific bf16 type in the AST is gated by:
```
bool ARMTargetInfo::hasBFloat16Type() const {
// The __bf16 type is generally available so long as we have any fp registers.
return HasBFloat16 || (FPU && !SoftFloat);
}
```
And the target we use when evaluating symbols (derived from the program
file, I think, haven't found it yet) does not enable any of this.
This means that we fall back to __fp16.
So for parts of the testing we just need to expect __fp16 instead, and
others we need to skip because now a class looks like it inherits from
itself.
There's a proper fix here somewhere but I don't know what it is yet.
