Remove the bom from the data

[akshita31]

Fixes: #2521

We were getting the red flame because of a mono behavior, where if we set the encoding to UTF8 then a BOM(Byte Object Mark) is pushed into the stream (output as well as error) as the first character. In the extension we were listening to this input on the error stream and making the flame red.

So the workaround is to remove the "BOM" from the buffer and firing the "STDERR" event only if the length of the BOM is greater than 0.

This will also remove the stray character in the "OmniSharp" log that appears when using mono on Linux/Mac.

[rchande]

It's worth noting that this is a mono behavior. A console app that does nothing but set Console.OutputEncoding = Encoding.UTF8 will print a BOM after the encoding is set.

[codecov]

Codecov Report

Merging #2540 into master will increase coverage by 0.07%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master    #2540      +/-   ##
==========================================
+ Coverage   65.26%   65.33%   +0.07%     
==========================================
  Files          96       97       +1     
  Lines        4203     4212       +9     
  Branches      602      603       +1     
==========================================
+ Hits         2743     2752       +9     
+ Misses       1291     1290       -1     
- Partials      169      170       +1

Flag	Coverage Δ
#integration	53.22% <83.33%> (-0.31%)	⬇️
#unit	84.67% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
src/utils/removeBOM.ts	100% <100%> (ø)
src/omnisharp/server.ts	71.67% <66.66%> (-0.06%)	⬇️
src/omnisharp/requestQueue.ts	81.81% <0%> (-3.04%)	⬇️
src/features/diagnosticsProvider.ts	76.81% <0%> (+2.17%)	⬆️

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