Removes vendoring and updates to Go 1.18 and latest fasthttp

[codefromthecrypt]

This updates to Go 1.18 and removes the vendor directory.

Per Go's release policy, Go 1.14 has been unsupported for a while.

This also updates to latest fasthttp so that mosn can support HTTP trailers.

see mosn/api#50
see mosn/mosn#2145 (comment)
see https://go.dev/doc/devel/release#policy

cc @taoyuanyuan

[codecov-commenter]

Codecov Report

Base: 45.73% // Head: 49.44% // Increases project coverage by +3.71% 🎉

Coverage data is based on head (4f68706) compared to base (949046a).
Patch coverage: 79.86% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #65      +/-   ##
==========================================
+ Coverage   45.73%   49.44%   +3.71%     
==========================================
  Files          48       56       +8     
  Lines        2683     2985     +302     
==========================================
+ Hits         1227     1476     +249     
- Misses       1374     1410      +36     
- Partials       82       99      +17     

Impacted Files	Coverage Δ
variable/protocolres.go	61.90% <61.90%> (ø)
variable/api.go	69.76% <69.76%> (ø)
variable/factory.go	73.17% <73.17%> (ø)
buffer/buffer.go	80.28% <80.28%> (ø)
variable/var.go	96.15% <96.15%> (ø)
buffer/bytebuffer_ctx.go	100.00% <100.00%> (ø)
buffer/log.go	50.00% <100.00%> (ø)
internal/context/context.go	100.00% <100.00%> (ø)
internal/context/wrapper.go	100.00% <100.00%> (ø)
log/logger.go	50.83% <0.00%> (-1.25%)	⬇️
... and 1 more

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[codefromthecrypt]

@taoyuanyuan can you re-kick CI, I tried with a newer version of the same lint job.

[taoyuanyuan]

LGTM