sagemathgh-40975: Workaround for linbox charpoly/minpoly issues, take 2

Fix sagemath#40974 by checking the
charpoly has the correct degree.

we unfortunately cannot do the same thing for minpoly, since we don't a
priori know its degree.

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- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

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URL: sagemath#40975
Reported by: user202729
Reviewer(s):

Author: Release Manager

build/pkgs/configure/checksums.ini

@@ -1,3 +1,3 @@
 tarball=configure-VERSION.tar.gz
-sha1=b36924b2391937313f3b2037eb1ffa4e3a9b2d81
-sha256=ec9a7a235593430352081443b1089403452ec349a202b2ca5cd73ceb63bbe26c
+sha1=85ea590bfb3ee849ba157ae43bf2ad0536d830a8
+sha256=90bd69bd4d7c5968b50a113abced92fe1f8250e5bc2ddfc64f7a48b729ffa199

build/pkgs/configure/package-version.txt

@@ -1 +1 @@
-0ef31d1493e6873bbdb7e14f91c57275ba3b20ee
+e7455996d0dc9114d649bdd5567394729cee799f

src/sage/matrix/matrix_integer_dense.pyx

@@ -1416,7 +1416,7 @@ cdef class Matrix_integer_dense(Matrix_dense):
                 sig_on()
                 linbox_fmpz_mat_charpoly(g._poly, self._matrix)
                 sig_off()
-                if g.lc() == 1:
+                if g.lc() == 1 and g.degree() == self._nrows:
                     break
         elif algorithm == 'generic':
             g = Matrix_dense.charpoly(self, var)

src/sage/matrix/matrix_integer_sparse.pyx

@@ -912,7 +912,7 @@ cdef class Matrix_integer_sparse(Matrix_sparse):
                 fmpz_poly_set_coeff_mpz(g._poly, i, tmp)
             _fmpz_poly_set_length(g._poly, p.size())
 
-            if g.lc() == 1:
+            if g.lc() == 1 and g.degree() == self._nrows:
                 break
 
         del M