Add namespace over fmtlib to avoid symbol conflicts

[Anilm3]

• Add ddwaf namespace over fmtlib to avoid symbol conflicts
• Remove unnecessary fmtlib code

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (55879e9) 83.23% compared to head (42ca068) 83.23%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #237   +/-   ##
=======================================
  Coverage   83.23%   83.23%           
=======================================
  Files         106      106           
  Lines        4176     4176           
  Branches     1914     1914           
=======================================
  Hits         3476     3476           
  Misses        279      279           
  Partials      421      421           

Flag	Coverage Δ
waf_test_none	83.13% <ø> (ø)
waf_test_sse2	83.20% <ø> (ø)

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