Fix for Windows Event Log operator in Windows Server 2022

[BinaryFissionGames]

This is a port of this fix from Stanza: observIQ/stanza#456

TL;DR of the issue:
The API for EvtFormatMessage returns number of characters written to the buffer, and each character is the Windows WCHAR type, which is 2 bytes. It seems like previous versions of Windows returned a much larger size back (greater than 2x) for how many characters it had written to the provided buffer, but with Windows Server 2022 we are seeing it return the correct value, leading to try to only parse half of the returned XML.

Resolves #284

[codecov]

Codecov Report

Merging #283 (1a2ee2c) into main (efb458e) will decrease coverage by 0.1%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##            main    #283     +/-   ##
=======================================
- Coverage   76.9%   76.8%   -0.2%     
=======================================
  Files         95      94      -1     
  Lines       4456    4410     -46     
=======================================
- Hits        3429    3389     -40     
+ Misses       707     701      -6     
  Partials     320     320             

Impacted Files	Coverage Δ
operator/builtin/input/tcp/tcp.go	78.0% <0.0%> (-1.7%)	⬇️