Re-visit From impl for native data types found in NBT data format.

[TerminatorNL]

Now no longer returns None but Result<> with the old value if the type did not match the desired type.

Related: #145 (comment)

[rj00a]

• The tag module is private to the crate. I think the NbtType trait and the generic type parameter on InvalidTypeError should be removed to keep the interface as simple as possible.
• InvalidTypeError is missing a std::error::Error impl.
• If TryFrom<Value> for T exists, it would make sense to me that TryFrom<&Value> for &T and TryFrom<&mut Value> for &mut T should also exist.
• It is worth looking at serde_json::Value. Notably, it does not have any trait impls to do Value to T conversions. The closest thing is the as_* methods.

To avoid the above problems, I think it would be best to just remove all the TryFrom<Value> for T and From<Value> for Option<T> impls on Value and recreate the needed conversion functions in valence_anvil. Or create an analogue of the as_* functions if that proves sufficient for your needs.

[TerminatorNL]

Have a look at the latest change. I have ditched all generics and hard-coded the value conversions as seen in serde. It created the following methods:

is_*(&self) -> bool
as_*(&self) -> Option<&*>
as_*_mut(&mut self) -> Option<&mut *>
take_*(self) -> Option<*>

IntelliJ IntelliSense works for all of the methods defined in the macro.

[TerminatorNL]

Woops, I wanted to rename the branch. Guess not!

[rj00a]

I think the take_* functions should be renamed to into_* since "take" implies that the argument is not consumed. Other than that, looks good to me.