refactor: timer

[George-Miao]

Closes #474

Some explanation in Chinese: https://t.me/compio_rs/26252. @kanarus could you please test with this branck again?

[kanarus]

@George-Miao It seems correctly working!

https://github.com/kanarus/test-compio-timeout/tree/fix/timeout-error

cargo run --features compio
   Compiling compio-buf v0.7.0 (https://github.com/George-Miao/compio?branch=fix%2Ftimeout-error#2cd512b4)
   Compiling compio-driver v0.9.0 (https://github.com/George-Miao/compio?branch=fix%2Ftimeout-error#2cd512b4)
   Compiling compio-fs v0.9.0 (https://github.com/George-Miao/compio?branch=fix%2Ftimeout-error#2cd512b4)
   Compiling compio-log v0.1.0 (https://github.com/George-Miao/compio?branch=fix%2Ftimeout-error#2cd512b4)
   Compiling compio-io v0.8.0 (https://github.com/George-Miao/compio?branch=fix%2Ftimeout-error#2cd512b4)
   Compiling compio-runtime v0.9.0 (https://github.com/George-Miao/compio?branch=fix%2Ftimeout-error#2cd512b4)
   Compiling compio-net v0.9.0 (https://github.com/George-Miao/compio?branch=fix%2Ftimeout-error#2cd512b4)
   Compiling compio v0.16.0 (https://github.com/George-Miao/compio?branch=fix%2Ftimeout-error#2cd512b4)
   Compiling test-compio-timeout v0.1.0 (/home/kanarus/projects/kanarus/test-compio-timeout)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.43s
     Running `target/debug/test-compio-timeout`
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[George-Miao]

We are still debating on whether this quick dirty fix is sufficient (it's an O(n) situation everytime a timer gets dropped so not really optimal).

[George-Miao]

We're refactoring the whole timer now, after some discussion

[Berrysoft]

LGTM