feat: alternate PRQL-native implementation of append by:name

[kgutwin]

See #5165 for background discussion.

This PR adds a PRQL-native implementation of append by:name which is dialect-independent. This is a counterpart (but not exclusive to) PR #6037 which would add dialect-specific support for UNION ALL BY NAME.

This PR has three main categories of changes:

1. The std._append_by_name function was added, and the internal definition of append was extended to parse the by: named argument. When by:name is provided, it generates a FuncCall expression to invoke std._append_by_name.
2. Support was added in semantic/resolver/expr.rs for wildcard expansion of relations via their lineage information. This seemed to be necessary in order to implement _param.bottom.* within the std._append_by_name function.
3. Two new tuple functions were added: tuple_uniq and tuple_reverse. I ended up not needing to use tuple_reverse but I left it in anyway in hopes that someone will find it useful. tuple_uniq takes a tuple which may have duplicate entries (by alias or by Ident name) and returns either the earliest or latest seen instance of a given name, depending on the value of the take: named argument.

Updates to the documentation are still pending, and there's also a potential question related to lineage that I may work on exploring.

[prql-bot]

Nice work — the _append_by_name formulation in std.prql is a clever, fully dialect-independent approach, and the column-alignment via tuple_uniq reads cleanly.

CI is red because Clippy runs with -D warnings and flags two issues, both in this diff (see inline suggestions):

• expr: &Box<pl::Expr> triggers clippy::borrowed_box — &pl::Expr works via deref coercion at the call site.
• The trailing return Err(...) in resolve_ident_wildcard triggers clippy::needless_return.

A couple of non-blocking notes for whenever you pick this back up (the PR description already flags docs/lineage as pending):

• tuple_reverse is added to std.prql and the resolver but, per the description, isn't used by anything. Adding it permanently expands the language surface speculatively — worth dropping it unless there's a concrete consumer, since it'd otherwise need docs/tests of its own.
• Several log::trace!/log::debug! calls and the new Module::all_names helper ("Useful for debugging") look like instrumentation left over from development (e.g. the per-ident ... candidates dump in expr.rs, the find_input_by_name trace in module.rs, the tuple-intersection trace in types.rs). They're trace-gated so harmless at runtime, but worth pruning the ones that were just for bring-up before merge.

[prql-bot]

Suggested change

	expr: &Box<pl::Expr>,
	expr: &pl::Expr,

clippy::borrowed_box fires here (CI -D warnings). &pl::Expr is sufficient — the call site passes &Box<Expr>, which deref-coerces.

[prql-bot]

Suggested change

	return Err(Error::new_simple(format!("Unknown relation {ident}")));
	Err(Error::new_simple(format!("Unknown relation {ident}")))

clippy::needless_return fires on this trailing return (CI -D warnings).