Fix TableKey / ObjKey conversion on Android x86

[DominicFrei]

Description

When retrieving TableKey and ObjKey from Core we interpret the returned values of type UInt32 and Int64 as TableKey and ObjKey without any conversion.

On Android x86 this leads to a misalignment in memory though since TableKey and ObjKey are structs which leads to a crash as described in #2456.

This PR reads the return values correctly and converts them in their corresponding Handle into the structs used on the .NET side.

N.B.: No further tests added. The problem that this was not caught by our tests is not the test suite itself but the fact that we do not test on Android x86 at the moment. As soon as such a device is added and run the current tests will implicitly apply.

In addition to that the hash code of objects is now calculated using table key in addition to just the object key (see #2473).

Fixes #2456
Fixes #2473

TODO

• Changelog entry
• Tests (if applicable)

[nirinchev]

Final nits, otherwise it looks good.

[nirinchev]

Do we need these std::hash-es here? Can we use table_key_value directly - maybe with a cast?

[DominicFrei]

I guess the normal way would be to only use them since they are already provided by the standard library but the other way round should be fine as well. Removed them.

[nirinchev]

Yeah, I'm not familiar with how C++ does things, so happy to use the idiomatic way there - it's just coming from C#, you would rarely use GetHashCode on a primitive type when you can just use the value itself.

[DominicFrei]

I did some more research now that you mention it. Good point about the primitives:
https://stackoverflow.com/questions/38304877/why-stdhashint-seems-to-be-identity-function
It makes sense but means that I can just remove it since std::hash<int>(i) == i anyway.

I'll just keep it our way then. There are certainly many more ways but if the current implementation is fine I guess we can just keep it.
I thought about just concatenating table key and object key since that would always lead to a unique 'hash':

auto table_key_value = object.obj().get_table()->get_key().value;
auto object_key_value = object.obj().get_key().value;

std::string concatenation = "" + table_key_value + object_key_value;
int hashCode = std::stoi(concatenation);

return hashCode;

[DominicFrei]

I had to add c249f25 since there was a valid warning on UWP:

'return': conversion from '__int64' to 'int32_t', possible loss of data

@nirinchev fyi + above comment about hashes.

It's just a tiny change, but I don't like merging unseen commits.

[nirinchev]

That warning is correct - -9999999769 is beyond what int32 can hold. This is what VS generated for a simple struct with table key and object key if you want to use it:

            public override int GetHashCode()
            {
                var hashCode = -986587137;
                hashCode = hashCode * -1521134295 + ObjKey.GetHashCode();
                hashCode = hashCode * -1521134295 + TableKey.GetHashCode();
                return hashCode;
            }