fix: align dotnet segment with other languages
feat: missing command text + json schema updated
chore: doc updated
perf: cache executable path
chore: not supported version icon updated(previus one was unreadable)
New segment for .NET SDK version (or unsupported version) display.
Includes update for handling command execution errors so segments
can act differently based on exit codes. Using a custom error
type to make it testable rather than passing the OS error directly
to the segment.