Update to use zero based indexes

[david-driscoll]

I'm moving forward with the lsp changes, but I figured this should land before that.

OmniSharp has a flag that tells the serializer to serialize with or without zero based indexes. Internally OmniSharp works purely on zero-based indexes because it makes interacting with Roslyn easier. However for backward compatibility externally we surface one-based indexes, the -z flag tells OmniSharp to return zero-based indexes instead of one based.

[JoeRobich]

@NTaylorMullen @ryanbrandenburg Would this break the location mapping performed by the Razor extension?

[david-driscoll]

Looking at the code it shouldn't all the middleware execution is done after everything is converted to vscode types, which are zero-based already.

[codecov]

Codecov Report

Merging #4300 (f0abf6f) into master (942a0cb) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4300   +/-   ##
=======================================
  Coverage   85.99%   85.99%           
=======================================
  Files          60       60           
  Lines        1857     1857           
  Branches      215      215           
=======================================
  Hits         1597     1597           
  Misses        200      200           
  Partials       60       60           

Flag	Coverage Δ
integration	100.00% <ø> (ø)
unit	85.99% <ø> (ø)

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[333fred]

Sorry I never ended up looking at this, I got distracted by a couple video games... LGTM though.