[mlir] Refactor alias generation to support nested aliases

We currently only support one level of aliases, which isn't great
in situations where an attribute/type can have multiple duplicated
components nested within it(e.g. debuginfo metadata). This commit
refactors alias generation to support nested aliases, which requires
changing alias grouping to take into account the depth of child
aliases, to ensure that attributes/types aren't printed before the
aliases they use.

The only real user facing change here was that we no longer print
0 as an alias suffix, which would be unnecessarily expensive to keep
in the new alias generation method (and isn't that valuable of a
behavior to preserve).

Differential Revision: https://reviews.llvm.org/D136541