Sockets Io Uring Multishot Reads And Write Backpressure

The :ref:io_uring <envoy_v3_api_field_extensions.network.socket_interface.v3.DefaultSocketInterface.io_uring_options> socket interface now supports :ref:multishot reads <envoy_v3_api_field_extensions.network.socket_interface.v3.IoUringOptions.enable_multishot_receive> backed by a kernel-provided buffer ring on Linux kernel 6.0 or later, and applies write backpressure through the new :ref:write_high_watermark_bytes <envoy_v3_api_field_extensions.network.socket_interface.v3.IoUringOptions.write_high_watermark_bytes> and :ref:write_low_watermark_bytes <envoy_v3_api_field_extensions.network.socket_interface.v3.IoUringOptions.write_low_watermark_bytes> options. The readv-based read path now grows its buffer adaptively for large transfers.