[🚀 Feature]: [dotnet] [bidi] Polymorphic static factory

### Description

Currently:

```csharp
await _context.LocateNodesAsync(new InnerTextLocator("Sign In"));
```

It is nice low-level implementation. Basically `LocateNodesAsync` method accepts abstract `Locator`. It means when user writes a code he doesn't know which well-known inherited classes from `Locator` he may use. This is common issue in .NET.

### Have you considered any alternatives or workarounds?

How to resolve: introduce static factory.
```csharp
await _context.LocateNodesAsync(Locator.InnerText("Sign In"));
```

Very simple and useful. What about optional parameters? It will be implicitly available via:
```csharp
await _context.LocateNodesAsync(Locator.InnerText("Sign In") with { IgnoreCase = true });
```