feat(assert): add idiomatic assertion capability

This commit implements the idiomatic assertion feature described
by Rouson et al. [1].  The leverages the machinery for writing
test-diagnosis expressions inspired by natural language and
supports the same for assertion diagnoses.  To accomplish this,
the commit adds

1. An assertion_diagnosis_t type that trivially extends Julienne's
   test_diagnosis_t type, i.e., without adding components or
   procedure bindings, and
2. A generic assert interface and corresponding julienne_assert
   subroutine, wherein
   a. The subroutine's interface body contains only one dummy
      argument: an assertion_diagnosis_t object and where
   b. The subroutine's definition contains only one executable
      statement: a call to the Assert dependency's "assert"
      subroutine.

[1] Rouson, D., Bonachea, D., and Rasmussen, K. (2025) "Idiomatic
    correctness-checking via Fortran 2023 using Julienne,"
    US-RSE '25, under review.

Author: rouson

src/julienne/julienne_assertion_s.f90

@@ -0,0 +1,15 @@
+submodule (julienne_test_diagnosis_m) julienne_assertion_diagnosis_s
+  use assert_m, only : assert_library_assert => assert
+  implicit none
+
+contains
+
+  module procedure construct_from_parent
+    assertion_diagnosis%test_diagnosis_t = test_diagnosis
+  end procedure
+
+  module procedure julienne_assert
+    call assert_library_assert(assertion_diagnosis%test_passed_, assertion_diagnosis%diagnostics_string_)
+  end procedure
+
+end submodule

src/julienne/julienne_test_diagnosis_m.F90

@@ -10,6 +10,8 @@ module julienne_test_diagnosis_m
 
   private
   public :: test_diagnosis_t
+  public :: assertion_diagnosis_t
+  public :: assert
   public :: operator(.all.)
   public :: operator(.and.)
   public :: operator(.approximates.)
@@ -30,6 +32,9 @@ module julienne_test_diagnosis_m
     procedure diagnostics_string
   end type
 
+  type, extends(test_diagnosis_t) :: assertion_diagnosis_t
+  end type
+
   integer, parameter :: default_real = kind(1.), double_precision = kind(1D0)
 
 #if HAVE_DERIVED_TYPE_KIND_PARAMETERS
@@ -47,6 +52,25 @@ module julienne_test_diagnosis_m
   end type
 #endif
 
+  interface assertion_diagnosis_t
+
+    pure module function construct_from_parent(test_diagnosis) result(assertion_diagnosis)
+      implicit none
+      type(test_diagnosis_t), intent(in) :: test_diagnosis
+      type(assertion_diagnosis_t) assertion_diagnosis
+    end function
+
+  end interface
+
+  interface assert
+
+    pure module subroutine julienne_assert(assertion_diagnosis)
+      implicit none
+      type(assertion_diagnosis_t), intent(in) :: assertion_diagnosis
+    end subroutine
+
+  end interface
+
   interface operator(.all.)
 
     pure module function aggregate_diagnosis(diagnoses) result(diagnosis)