Fix issues with repeated enums with unique, defined_only, in and not_in for cc and go

[fishcakez]

When trying to use repeated enums with unique, defined_only, in or not_in encountered issues with cc and go implementations.

For go, the generated code for repeated enum when using defined_only could be incorrect when importing enums from multiple packages with name collisions. The imports are correct (e.g. _go, _go1) but the defined check would always use the first case (e.g. _go). The test added will fail to compile without the fix:

undefined: _go.DeepEnum_name

For cc, then generated code for repeated enum when using unique has issue with const_cast from int -> enum. Therefore for repeated unique enum use set of int to avoid cast/reference wrapper. The tested added will fail to compile without the fix:

error: invalid 'const_cast' from type 'const int*' to type 'tests::harness::cases::AnEnum*'
  664 |                                 auto p = _RepeatedUniqueEnum_Val_Unique.emplace(const_cast<AnEnum&>(item));

For cc, the generated code for repeated enum when using in or not_in has incorrect namespace where :: separator is not used, and instead _ is. Therefore use correct package name helper for cc. The test added will fail to compile without the fix:

error: 'nested' was not declared in this scope; did you mean 'tests::harness::cases::other_package::nested'?
 1249 |         const std::set<nested::DeepEnum> _RepeatedExternalEnumMultiLevel_Foo_InLookup = {

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