feat: Reimplement v5 with old `EventLoop` design

[de-sh]

Closes #463

Doesn't yet support user properties, and or topic aliasing

Tests performed

• Ran examples/asyncpubsub_v5 against mosquitto broker, connection successful over v5 protocol:

1664084176: New client connected from ::1:49112 as test-1 (p5, c1, k5).
1664084176: No will message specified.
1664084176: Sending CONNACK to test-1 (0, 0)
1664084176: Received SUBSCRIBE from test-1
1664084176: 	hello/world (QoS 0)
1664084176: test-1 0 hello/world
1664084176: Sending SUBACK to test-1
1664084176: Received PUBLISH from test-1 (d0, q2, r0, m2, 'hello/world', ... (1 bytes))
1664084176: Sending PUBREC to test-1 (m2, rc0)
1664084176: Received PUBREL from test-1 (Mid: 2)
1664084176: Sending PUBLISH to test-1 (d0, q0, r0, m0, 'hello/world', ... (1 bytes))
1664084176: Sending PUBCOMP to test-1 (m2)
1664084177: Received PUBLISH from test-1 (d0, q2, r0, m3, 'hello/world', ... (2 bytes))
1664084177: Sending PUBREC to test-1 (m3, rc0)
1664084177: Received PUBREL from test-1 (Mid: 3)
1664084177: Sending PUBLISH to test-1 (d0, q0, r0, m0, 'hello/world', ... (2 bytes))
1664084177: Sending PUBCOMP to test-1 (m3)
1664084178: Received PUBLISH from test-1 (d0, q2, r0, m4, 'hello/world', ... (3 bytes))
1664084178: Sending PUBREC to test-1 (m4, rc0)
1664084178: Received PUBREL from test-1 (Mid: 4)
1664084178: Sending PUBLISH to test-1 (d0, q0, r0, m0, 'hello/world', ... (3 bytes))
1664084178: Sending PUBCOMP to test-1 (m4)
1664084178: Client test-1 closed its connection.

P.S: will maintain new EventLoop architecture in restructure branch