Implement missing Tree APIs

[ensi321]

Here are the ones used by lodestar's beacon-node and state-transition (including those that are used in upcoming glamsterdam). List might be non-exhaustive:

• ListCompositeTreeViewDU.sliceFrom()
• ListCompositeTreeViewDU.getAll()
• ListCompositeTreeViewDU.sliceTo()
• ListBasicTreeViewDU.push()
• ListBasicTreeViewDU.sliceTo()
• ContainerTreeViewDUType.serialize()
• ContainerTreeViewDUType.deserialize()
• ContainerTreeViewDUType.toValue()
• ContainerTreeViewDUType.type.tree_serializedSize()
• ContainerTreeViewDUType.defaultViewDU()
• TreeViewDU.clone()
• TreeViewDU.serializeToBytes()
• ListCompositeTreeViewDU.push()
• BitArrayTreeViewDU.toBoolArray()

Prerequisite of #20