spack diff: make output order deterministic (#25169)

The output order for `spack diff` is nondeterministic for larger diffs -- if you
ran it several times it will not put the fields in the spec in the same order on
successive invocations.

This makes a few fixes to `spack diff`:

- [x] Implement the change discussed in https://github.com/spack/spack/pull/22283#discussion_r598337448
      to make `AspFunction` comparable in and of itself and to eliminate the need for `to_tuple()`

- [x] Sort the lists of diff properties so that the output is always in the same order.

- [x] Make the output for different fields the same as what we use in the solver. Previously, we
      would use `Type(value)` for non-string values and `value` for strings.  Now we just use
      the value.  So the output looks a little cleaner:

      ```
      == Old ==========================        == New ====================
      @@ node_target @@                        @@ node_target @@
      -  gdbm Target(x86_64)                   -  gdbm x86_64
      +  zlib Target(skylake)                  +  zlib skylake
      @@ variant_value @@                      @@ variant_value @@
      -  ncurses symlinks bool(False)          -  ncurses symlinks False
      +  zlib optimize bool(True)              +  zlib optimize True
      @@ version @@                            @@ version @@
      -  gdbm Version(1.18.1)                  -  gdbm 1.18.1
      +  zlib Version(1.2.11)                  +  zlib 1.2.11
      @@ node_os @@                            @@ node_os @@
      -  gdbm catalina                         -  gdbm catalina
      +  zlib catalina                         +  zlib catalina
      ```

I suppose if we want to use `repr()` in the output we could do that and could be
consistent but we don't do that elsewhere -- the types of things in Specs are
all stringifiable so the string and the name of the attribute (`version`, `node_os`,
etc.) are sufficient to know what they are.

0 files changed, 0 insertions, 0 deletions