Dynamic Modules Added A Transport Socket Extension

Added a new dynamic modules transport socket extension (envoy.transport_sockets.dynamic_modules) that delegates connection I/O to a transport socket implemented in a dynamic module loaded via dlopen. The module performs raw socket reads and writes through io_read and io_write callbacks and transforms the bytes that flow over the connection, for example to implement a custom encryption scheme. The module can also negotiate secure transport for the STARTTLS pattern and inspect the connection's local and remote addresses. The extension can be configured on both downstream listeners and upstream clusters. The Rust SDK exposes this through a TransportSocket interface and a matching transport socket init function. See :ref:DynamicModuleTransportSocket <envoy_v3_api_msg_extensions.transport_sockets.dynamic_modules.v3.DynamicModuleTransportSocket> for configuration details.