feat(qp): introduce ModifyQueuePairError and PostSendError

[dragonJACson]

RDMA C functions basically use return value (when it could be used) for returning an errno, or when sometimes the function should return a pointer but return a NULL, user should read errno themselves.

Most of the time, the errno actually suggests an error from kernel, users really need a lot of experience on RDMA to understand what's going wrong by just read a simple 8bit error number.

RDMAmojo and rdma-core man pages provides some hints on errnos, while that need users to search and grab. Rust provides a powerful error handling system, why not just integrate the hints with errno together, plus some context to build our error types? I provide a trial implementation in this commit.

Sometimes the complicated error types introduce performance penalty, so I make it optional.

Related issue: #3

[codecov]

Codecov Report

Attention: Patch coverage is 7.35294% with 63 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/verbs/queue_pair.rs	7.35%	63 Missing ⚠️

Files with missing lines	Coverage Δ
src/verbs/queue_pair.rs	71.49% <7.35%> (-6.31%)	⬇️

[dragonJACson]

Some examples:

$ ./target/debug/examples/rc_pingpong -d mlx5_0 -n 10 -s 2400 -m 256 -g 1 127.0.0.1
 local address: QPN 0x0326, PSN 0x8088ba, GID fe80:0000:0000:0000:e46d:faff:fefa:6bcb
remote address: QPN 0x0325, PSN 0xf49e1a, GID fe80:0000:0000:0000:e46d:faff:fefa:6bcb
Error: network unreachable, source gid index: 1, destination gid: fe80:0000:0000:0000:e46d:faff:fefa:6bcb

Caused by:
    No route to host (os error 113)

$ ./target/debug/examples/rc_pingpong -n 10 -s 2400 -m 256 -d mlx5_0 127.0.0.1 -g 1
Error: invalid transition from Reset to Init, possible invalid masks QueuePairAttributeMask[], possible needed masks QueuePairAttributeMask[AccessFlags, Port]

Caused by:
    Invalid argument (os error 22)

cc @FujiZ