Changelog #348

#23464 (first contribution) use sub-unification roots in type_var_is_sized.

#23462 (first contribution) offer "Generate variant" on Self.

#23468 offer let and letm completions in arm and closure expressions.

#23197 some small cleanups and micro-optimizations.

#23196 don’t lower the same types twice hir-ty.

#23419 don’t compute hover information for SCIP.

#23448, #23449, #23455 pin unicode-ident.