Auto merge of #17586 - ShoyuVanilla:tuple-arg-macro-rest, r=Veykril

Allow macro expansions into `RestPat` in tuple args work as ellipsis like plain `RestPat`

Fixes #17292

Currently, Rust Analyzer lowers `ast::Pat::RestPat` into `Pat::Missing` in general cases on the following lines;

https://github.com/rust-lang/rust-analyzer/blob/ffbc5ad993d5cd2f3b8bcf9a511165470944ab91/crates/hir-def/src/body/lower.rs#L1359-L1367

And in some proper positions such as `TupleStruct(..)`, it is specially handed on the following lines;

https://github.com/rust-lang/rust-analyzer/blob/ffbc5ad993d5cd2f3b8bcf9a511165470944ab91/crates/hir-def/src/body/lower.rs#L1429-L1437

This behavior is reasonable because rustc does similar things in
https://github.com/rust-lang/rust/blob/62c068feeafd1f4abbf87243d69cf8862e4dd277/compiler/rustc_ast_lowering/src/pat.rs#L108-L111
and
https://github.com/rust-lang/rust/blob/62c068feeafd1f4abbf87243d69cf8862e4dd277/compiler/rustc_ast_lowering/src/pat.rs#L123-L142

But this sometimes works differently because Rust Analyzer expands macros while ast lowering;

https://github.com/rust-lang/rust-analyzer/blob/ffbc5ad993d5cd2f3b8bcf9a511165470944ab91/crates/hir-def/src/body/lower.rs#L1386-L1398
https://github.com/rust-lang/rust-analyzer/blob/ffbc5ad993d5cd2f3b8bcf9a511165470944ab91/crates/hir-def/src/body/lower.rs#L941-L963
but rustc uses expanded ast in the corresponding tuple-handling process, so it does not have macro patterns there.
https://github.com/rust-lang/rust/blob/62c068feeafd1f4abbf87243d69cf8862e4dd277/compiler/rustc_ast_lowering/src/pat.rs#L114

So, if a macro expansion in a tuple arg results in `..`, rustc permits it like plain `..` pattern, but Rust Analyzer rejects it.
This is the root cause of #17292 and this PR allows macros expanded into `..` in a tuple arg position work as ellipsis like that.

Author: bors