Address gosec and staticcheck linter warnings

[asnyatkov]

Description

Add nolint directives for safe integer conversions and slice accesses that are already bounds-checked. Replace WriteString(Sprintf(...)) with Fprintf.

[JoTurk]

Thank you, this is related to our lint upgrade can you do it in #356

for reference we update our lint settings like this pion/dtls#803

in the next upgrade we're going to split settings so it doesn't break repos until we upgrade,
I'll invite you to the org so you can push commits to the branch directly

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.59%. Comparing base (e119a01) to head (319e178).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #358   +/-   ##
=======================================
  Coverage   82.59%   82.59%           
=======================================
  Files          28       28           
  Lines        3430     3430           
=======================================
  Hits         2833     2833           
  Misses        427      427           
  Partials      170      170           

Flag	Coverage Δ
go	82.59% <100.00%> (ø)

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