refactor: simplify Networkwith Framed<.., Codec>

[de-sh]

As discussed in #814 this simplifies Network using Framed and Codec

Type of change

• mqttbytes::Error is no longer Clone, Copy, PartialEq, Eq and 2 new variants, for io and packet size limit
• Refactors different parts of the codebase to regularize and simplify.
• Deprecates bulk read and moves write buffer into Network, which might lead to issues with packets in the buffer being dropped when an error is faced. But this seems like premature-optimization to be frank

Checklist:

• Formatted with cargo fmt
• Make an entry to CHANGELOG.md if it's relevant to the users of the library. If it's not relevant mention why.

[coveralls]

Pull Request Test Coverage Report for Build 8346655192

Details

• 274 of 519 (52.79%) changed or added relevant lines in 18 files are covered.
• 74 unchanged lines in 7 files lost coverage.
• Overall coverage decreased (-0.3%) to 37.53%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
rumqttc/src/mqttbytes/mod.rs	0	1	0.0%
rumqttc/src/v5/mqttbytes/mod.rs	0	1	0.0%
rumqttc/src/framed.rs	19	21	90.48%
rumqttc/src/mqttbytes/v4/codec.rs	29	31	93.55%
rumqttc/src/proxy.rs	0	3	0.0%
rumqttc/src/tls.rs	0	3	0.0%
rumqttc/src/mqttbytes/v4/connack.rs	0	6	0.0%
rumqttc/src/v5/mqttbytes/v5/connect.rs	0	6	0.0%
rumqttc/src/v5/mqttbytes/v5/ping.rs	0	6	0.0%
rumqttc/src/v5/mqttbytes/v5/codec.rs	22	31	70.97%

Files with Coverage Reduction	New Missed Lines	%
rumqttc/src/lib.rs	1	64.32%
rumqttc/src/mqttbytes/mod.rs	3	86.27%
rumqttc/src/v5/state.rs	5	68.42%
rumqttc/src/state.rs	11	79.36%
rumqttc/src/mqttbytes/v4/pubcomp.rs	18	8.33%
rumqttc/src/mqttbytes/v4/pubrel.rs	18	8.11%
rumqttc/src/mqttbytes/v4/pubrec.rs	18	8.11%

Totals
Change from base Build 8243857492:	-0.3%
Covered Lines:	6239
Relevant Lines:	16624

---

💛 - Coveralls

[flxo]

Nice. I appreciate the introduction of Framed!

The PR is definitely a step into right direction but I completely miss the batching topic discussed in #810.

Furthermore this patch removes the previously implemented batch sending of packets that are generated in response to incoming frames. The current implementation queues up to 10 packets before calling flush. This PR flushes the response after every processed incoming frame. I haven't profiled but this definitely has a negative performance impact.

Calling Network::send results in a SinkExt::send (impled by Framed). This is basically a poll_ready + start_send + poll_flush. This results in a sendto or similar sys call per packet.

To get back proper batching of outgoing frames there should made use of SinkExt::feed in a limited loop + SinkExt::flush. Think I demonstrated this here.

Is there a follow up to this PR already planned?

[de-sh]

Is there a follow up to this PR already planned?

Thanks for the suggestions, have opened #826 to resolve this, please review!

[de-sh]

Merging this, no functional changes included in this PR

[xiaocq2001]

After it's merged, some incoming messages disappear in event loop, please help to check.

asyncpubsub_v5 output before the merge:

     Running `target/debug/examples/asyncpubsub_v5`
Event = Incoming(ConnAck(ConnAck { session_present: false, code: Success, properties: Some(ConnAckProperties { session_expiry_interval: None, receive_max: Some(20), max_qos: None, retain_available: None, max_packet_size: None, assigned_client_identifier: None, topic_alias_max: Some(10), reason_string: None, user_properties: [], wildcard_subscription_available: None, subscription_identifiers_available: None, shared_subscription_available: None, server_keep_alive: None, response_information: None, server_reference: None, authentication_method: None, authentication_data: None }) }))
Event = Outgoing(Subscribe(1))
Event = Outgoing(Publish(2))
Event = Incoming(SubAck(SubAck { pkid: 1, return_codes: [Success(AtMostOnce)], properties: None }))
Event = Outgoing(PubRel(2))
Event = Incoming(PubRec(PubRec { pkid: 2, reason: Success, properties: None }))
Event = Incoming(Publish(Publish { dup: false, qos: AtMostOnce, retain: false, topic: b"hello/world", pkid: 0, payload: b"\x01", properties: None }))

asyncpubsub_v5 output after merge:

     Running `target/debug/examples/asyncpubsub_v5`
Event = Incoming(ConnAck(ConnAck { session_present: false, code: Success, properties: Some(ConnAckProperties { session_expiry_interval: None, receive_max: Some(20), max_qos: None, retain_available: None, max_packet_size: None, assigned_client_identifier: None, topic_alias_max: Some(10), reason_string: None, user_properties: [], wildcard_subscription_available: None, subscription_identifiers_available: None, shared_subscription_available: None, server_keep_alive: None, response_information: None, server_reference: None, authentication_method: None, authentication_data: None }) }))
Event = Outgoing(Subscribe(1))
Event = Outgoing(Publish(2))
Event = Outgoing(Publish(3))
Event = Outgoing(Publish(4))

[de-sh]

Thanks for pointing this out @xiaocq2001 there is the lack of a good testsuite for v5, might be a good issue to open!