65c807e695
This patch allows expressions to reference entities in anonymous
namespaces. Previously this would have resulted in:
```
(lldb) expr foo::FooAnonymousVar
error: <user expression 0>:1:6: no member named 'FooAnonymousVar' in namespace 'foo'
1 | foo::FooAnonymousVar
| ~~~~~^
```
We already allow such lookups through inline namespaces, and for the
purposes of lookup, anonymous namespaces shouldn't behave any different.
Fixes https://github.com/llvm/llvm-project/issues/96963.