gpu-compute,mem-ruby: Refactor GPU coalescer

gpu-compute,mem-ruby: Refactor GPU coalescer

Remove the read/write tables and coalescing table and introduce a two
levels of tables for uncoalesced and coalesced packets. Tokens are
granted to GPU instructions to place in uncoalesced table. If tokens
are available, the operation always succeeds such that the 'Aliased'
status is never returned. Coalesced accesses are placed in the
coalesced table while requests are outstanding. Requests to the same
address are added as targets to the table similar to how MSHRs
operate.

Change-Id: I44983610307b638a97472db3576d0a30df2de600
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27429
Reviewed-by: Bradford Beckmann <brad.beckmann@amd.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Bradford Beckmann <brad.beckmann@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>