@Flag properties that begin with "v" do not work.

I had a "verbose" flag for log output, but it was getting completely ignored and failed silently.

**ArgumentParser version:** `1.0.2`
**Swift version:**
```
swift-driver version: 1.26.9 Apple Swift version 5.5.1 (swiftlang-1300.0.31.4 clang-1300.0.29.6)
Target: arm64-apple-macosx12.0
```

### Checklist
- [ ] If possible, I've reproduced the issue using the `main` branch of this package
- [x] I've searched for [existing GitHub issues](https://github.com/apple/swift-argument-parser/issues)

### Steps to Reproduce

Create your own `ParsableCommand` with a flag such as:
```
struct MyCommand: ParsableCommand {

// other boilerplate here.

@Flag(name: .shortAndLong, help: "Whether to enable verbose logging.")
var verbose = false

mutating func run() throws {
print("Verbose Logging Enabled: \(self.verbose)") // is ALWAYS false.

// the rest of what you do here.
}
}
```
If you include this flag in your command line arguments, it is not parsed as expected.

### Expected behavior
The Flag should be set to true when you `swift run MyCommand --verbose`

Stretch goal: The compiler should fail or complain or warn about your variable name.

### Actual behavior
The argument --verbose is ignored and "fails silently"

### Workaround

make a custom flag name that doesn't begin with "v". In this case "fatlog" did the trick.

Start with the reported ParsableCommand example and its @Flag(name: .shortAndLong) property, then run it with --verbose to confirm the flag remains false. Trace how the flag is parsed and add a regression check showing that --verbose sets verbose to true; the issue is fixed when that behavior works without the workaround name.

Written by the indexing model from the issue text.