cmd/internal/objabi, runtime: compact FUNCDATA indices

As we deleted register maps, move FUNCDATA indices of stack
objects, inline trees, and open-coded defers earlier.

Change-Id: If73797b8c11fd207655c9498802fca9f6f9ac338
Reviewed-on: https://go-review.googlesource.com/c/go/+/265761


Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>