Version Flag Race

Fixed data race in --version flag parsing under concurrent CLI invocations

When multiple Terragrunt CLI invocations ran concurrently in the same process, urfave/cli/v2's package-level VersionFlag singleton was mutated concurrently by each invocation's flag-parsing path, producing a WARNING: DATA RACE on shared flag state.

Terragrunt now sets cli.App.HideVersion = true at construction, which prevents urfave from auto-appending its shared VersionFlag into each App's flag set. The --version / -v flag is unchanged from the user's perspective — it is handled by Terragrunt's own flag registered in internal/cli/flags/global.NewHelpVersionFlags.