* Add support for providing a custom ConnectionID generator via Config
This work makes it possible for servers or clients to control how
ConnectionIDs are generated, which in turn will force peers in the
connection to use those ConnectionIDs as destination connection IDs when sending packets.
This is useful for scenarios where we want to perform some kind
selection on the QUIC packets at the L4 level.
* add more doc
* refactor populate config to not use provided config
* add an integration test for custom connection ID generators
* fix linter warnings
Co-authored-by: Marten Seemann <martenseemann@gmail.com>
