Describe the feature

Implement a HIR builder that constructs HIR nodes using a bunch of helper methods.

Example:

pub struct HirBuilder<'hir> { /* ... */ }
impl<'hir> HirBuilder<'hir> {
    pub fn expr(&self, kind: hir::ExprKind<'hir>) -> hir::Expr<'hir> { /* ... */ }
}

An initial goal for this would be to replace the manual HIR node construction when desugaring loops and creating variables' getter functions, adding the necessary methods along the way.

Additional context

No response