Currently only BsonClassMapSerializer uses a Trie to speed up deserialization (by replacing element name UTF8 decoding/dictionary lookup with a single fast Trie lookup).

All our serializers should use a Trie.

Create a centralized place that encapsulates all of the following standard behavior:

1. Setting up a Trie for fast element name decoding
2. Looping over elements in a document during deserialization using the Trie
3. Support out of order elements
4. Standardize handling of invalid and missing elements