AnyValue refactor

Added

• AnyVec now can work with AnyValueSizeless.
• any_value::traits prelude.

Optimized

• AnyValue- family downcast now use provided type for compile-time optimization,
  instead of potentially unknown underlying type (which disabled optimization technique).

Breaking Changes

• AnyValue + AnyValueUnknown traits broken down into:
  • AnyValueUnknown -> AnyValueTypeless.
  • Introduced AnyValueSizeless - AnyValue that does know size and type.
  • Added any_value::move_out, any_value::move_out_w_size helpers.
• Changed AnyValueRaw non-owning wrappers names:
  • AnyValueRawUnknown -> AnyValueTypelessRaw.
  • Introduced AnyValueSizelessRaw.