DynamicParameters.AddParameters(IDbCommand): identity-free self-apply

[mgravell]

The full bag protocol — per-parameter DbType/direction/size/precision/scale, templates, literal replacement, RemoveUnused — already lives in AddParameters(command, identity), but the identity requirement makes it uncallable from outside: Identity's constructor is internal, and identity.Sql is consumed on the first line. This overload builds the identity from the command's own text and type (which is what identity.Sql is in practice), letting external tooling apply a parameter bag without reimplementing the protocol.

The immediate consumer is Dapper.AOT: its generated command factories can now support DynamicParameters arguments by delegating to the bag itself — which gives exact vanilla behavior for the whole surface (including Get<T> output reads and IParameterCallbacks) because it is the vanilla implementation. The generator probes for this symbol, so it activates only when the referenced Dapper has it; no coordination needed on release timing.

Test covers the bag + literal-replacement composition against a closed connection (no database needed). API registered in PublicAPI.Unshipped.txt.

[mgravell]

Pushed a follow-up: the overload now dispatches via (SqlMapper.IDynamicParameters)this rather than calling the protected method directly. A subclass that hides AddParameters and re-implements the interface — the DynamicParameterWithIntTVP pattern from this repo's own test suite — was otherwise skipped, because the direct call binds statically to the base method. Test added for the hiding-subclass shape.