[LifetimeSafety] Mark lifetime safety LangOptions as `Benign` (#204316)

Without this, we cannot load modules built without lifetime safety.
Analysis options are in general benign and does not effect AST
construction.

See doc:
```cpp
  /// For ASTs produced with different option value, signifies their level of
  /// compatibility.
  enum class CompatibilityKind {
    /// Does affect the construction of the AST in a way that does prevent
    /// module interoperability.
    NotCompatible,
    /// Does affect the construction of the AST in a way that doesn't prevent
    /// interoperability (that is, the value can be different between an
    /// explicit module and the user of that module).
    Compatible,
    /// Does not affect the construction of the AST in any way (that is, the
    /// value can be different between an implicit module and the user of that
    /// module).
    Benign,
  };
```