Times spec building and timing to public concretizer API (#47310)

This PR has two small contributions:
- It adds another phase to the timer for concrectization, "construct_specs", to actually see the time the concretizer spends interpreting the `clingo` output to build the Python object for a concretized spec. 
- It adds the method `Solver.solve_with_stats` to expose the timers that were already in the concretizer to the public solver API. `Solver.solve` just becomes a special case of `Solver.solve_with_stats` that throws away the timing output (which is what it was already doing).  

These changes will make it easier to benchmark concretizer performance and provide a more complete picture of the time spent in the concretizer by including the time spent interpreting clingo output.

lib/spack/spack/solver/asp.py

@@ -889,6 +889,7 @@ def on_model(model):
         result.satisfiable = solve_result.satisfiable
 
         if result.satisfiable:
+            timer.start("construct_specs")
             # get the best model
             builder = SpecBuilder(specs, hash_lookup=setup.reusable_and_possible)
             min_cost, best_model = min(models)
@@ -913,7 +914,8 @@ def on_model(model):
 
             # record the possible dependencies in the solve
             result.possible_dependencies = setup.pkgs
-
+            timer.stop("construct_specs")
+            timer.stop()
         elif cores:
             result.control = self.control
             result.cores.extend(cores)
@@ -4191,7 +4193,7 @@ def _check_input_and_extract_concrete_specs(specs):
                 spack.spec.Spec.ensure_valid_variants(s)
         return reusable
 
-    def solve(
+    def solve_with_stats(
         self,
         specs,
         out=None,
@@ -4202,6 +4204,8 @@ def solve(
         allow_deprecated=False,
     ):
         """
+        Concretize a set of specs and track the timing and statistics for the solve
+
         Arguments:
           specs (list): List of ``Spec`` objects to solve for.
           out: Optionally write the generate ASP program to a file-like object.
@@ -4213,15 +4217,22 @@ def solve(
           setup_only (bool): if True, stop after setup and don't solve (default False).
           allow_deprecated (bool): allow deprecated version in the solve
         """
-        # Check upfront that the variants are admissible
         specs = [s.lookup_hash() for s in specs]
         reusable_specs = self._check_input_and_extract_concrete_specs(specs)
         reusable_specs.extend(self.selector.reusable_specs(specs))
         setup = SpackSolverSetup(tests=tests)
         output = OutputConfiguration(timers=timers, stats=stats, out=out, setup_only=setup_only)
-        result, _, _ = self.driver.solve(
+        return self.driver.solve(
             setup, specs, reuse=reusable_specs, output=output, allow_deprecated=allow_deprecated
         )
+
+    def solve(self, specs, **kwargs):
+        """
+        Convenience function for concretizing a set of specs and ignoring timing
+        and statistics. Uses the same kwargs as solve_with_stats.
+        """
+        # Check upfront that the variants are admissible
+        result, _, _ = self.solve_with_stats(specs, **kwargs)
         return result
 
     def solve_in_rounds(