reserved type names being used in CSharp generation

[baywet]

if you have a schema named integer, kiota will generate a model for that in CSharp. The issue is that is conflicts with the type name under System. We already have excluded the shorthands (like int) but it's not enough. @andrueastman would you mind putting together a PR to exclude type names under system please so we don't have conflicts?

[andrueastman]

Acknowledging this one @baywet