feat: more conversion

[blckngm]

Implement more conversion traits to make entities easier to build/use (close #63):

• FooOpt from Foo
• FooArray from/into [Foo; n]
• FooArray TryFrom &[Foo]
• Union entity from item
• Vec FromIterator item
• ByteArray from/into [u8; n]
• ByteArray TryFrom &[u8]
• ByteArrayReader Into &[u8; n]
• ByteVec FromIterator u8

So instead of e.g.

.foo_opt(FooOpt::new_builder().set(Some(foo)).build())
.foo_vec(FooVec::new_builder().extend(foo_iter).build())
.foo_union(FooUnion::new_builder().set(foo).build())

we can use:

.foo_opt(foo.into())
.foo_vec(foo_iter.collect())
.foo_union(foo.into())

It's also easier to work with e.g. Uint32: 3u32.to_le_bytes().into(), u32::from_le_bytes(x.into()).

[blckngm]

@quake @yangby-cryptape Would you review this?

[quake]

LGTM, there is an unit test CI error, @blckngm could you resolve it?

[blckngm]

It's due to rust version used. Should be fixed now.

[yangby-cryptape]

Works well as it described.