Fix Derived in heat_geodesics; boost url (#2440)

* PlainObject -> MatrixBase

* template igl::Hit

* vector input intersect rays with multiple hits

* initialize

* initialize

* only write if hit

* fix templates

* template me baby

* templates

* my god. so many PlainObject -> Matrix; Derived -> PlainMatrix<Derived>

* Options doesn't exist for Maps/Refs

* templates; windows size_t shinanigans

* Derived->PlainMatrix

* windows template

* derived -> plainvector

* options

* fix templating

* std types

* fix windingnumbertree tempalting

* further fix windingnumbertree tempalting

* Xi->XI

* templating

* clean up and template some of the decimation code; eventually gave up on templating outer functions

* rm needless cast

* attempt to fix index templating in boolean code

* remove debugging casts

* more templatin hell

* debug kruft

* vector resize

* assert

* int -> template

* int -> template

* int -> template

* templating away more Xi

* templating away more 3i

* formatting

* vector

* plainmatrix

* plainmatrix

* bug

* templating MSH io

* remove use of Map

* zero default tags

* bug fix

* file debug flags

* __1::

* better typing

* knn tempalte

* note

* templating

* reorder scaf inputs

* fix build

* doc

* templates

* messier than I thought

* doc

* Xi -> XI

* use templated type

* 1x1 is always symmetric

* use index type

* split intrinsic

* templating

* template internal

* restore boost link

* actually add the change to hg

cmake/recipes/external/boost.cmake

@@ -12,7 +12,7 @@ include(FetchContent)
 # Define the Boost library to fetch
 FetchContent_Declare(
     Boost
-    URL https://boostorg.jfrog.io/artifactory/main/release/1.86.0/source/boost_1_86_0.tar.gz
+    URL https://archives.boost.io/release/1.86.0/source/boost_1_86_0.tar.gz
     URL_HASH MD5=ac857d73bb754b718a039830b07b9624
 )
 # Fetch Boost

include/igl/heat_geodesics.cpp

@@ -12,6 +12,7 @@
 #include "cotmatrix.h"
 #include "intrinsic_delaunay_cotmatrix.h"
 #include "massmatrix.h"
+#include "PlainVector.h"
 #include "massmatrix_intrinsic.h"
 #include "grad_intrinsic.h"
 #include "boundary_facets.h"
@@ -83,7 +84,7 @@ IGL_INLINE bool igl::heat_geodesics_precompute(
         return false;
       }
     }
-    const DerivedV M_diag_tr = M.diagonal().transpose();
+    const Eigen::Matrix<Scalar,1,Eigen::Dynamic> M_diag_tr = M.diagonal().transpose();
     const Eigen::SparseMatrix<Scalar> Aeq = M_diag_tr.sparseView();
     L *= -0.5;
     if(!igl::min_quad_with_fixed_precompute(