update deps + loosen some requirements

[melekes]

rules:

• for crates that are below v1.0 -> specify the precise version
• If the code uses a feature that was added for example in X 0.3.17,
  then you should specify 0.3.17, which actually means "0.3.y where y >=
  17"
• for crates the are above or equal v1.0 -> specify only major version
  if the crate's API is minimal and won't change between minor versions
  OR specify major&minor versions otherwise

tested with https://github.com/taiki-e/cargo-minimal-versions

[codecov]

Codecov Report

Merging #20 (c7e627c) into main (2d193c0) will decrease coverage by 19.54%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             main      #20       +/-   ##
===========================================
- Coverage   45.77%   26.22%   -19.55%     
===========================================
  Files          28       28               
  Lines        3216     6238     +3022     
  Branches     1392     2223      +831     
===========================================
+ Hits         1472     1636      +164     
- Misses        305     3009     +2704     
- Partials     1439     1593      +154     

Impacted Files	Coverage Δ
src/conn/conn_bridge.rs	44.88% <ø> (ø)
build.rs	25.00% <0.00%> (-25.00%)	⬇️
src/error.rs	2.54% <0.00%> (-9.00%)	⬇️
src/lib.rs	4.93% <0.00%> (-7.57%)	⬇️
src/buffer/buffer_test.rs	23.39% <0.00%> (-2.39%)	⬇️
src/vnet/conn/conn_test.rs	54.23% <0.00%> (+0.84%)	⬆️
src/conn/conn_udp_listener.rs	63.05% <0.00%> (+1.27%)	⬆️

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