Modular Boost and big CI update.

* Make the library modular usable.

* Add missing import-search for cconfig/predef checks.

* Add requires-b2 check to top-level build file.

* Bump B2 require to 5.2

* Remove boost-root target refs.

* Change all <source> references to <library>.

* Update copyright dates.

* Fix library global (relative) references.

* Move inter-lib dependencies to a project variable and into the build targets.

* Add Boost.StaticAssert transitive dep module.

* Only test on latest macOS.

* Add Boost.ThrowExceptions transitive dep module.

* Add Boost.Preprocessor transitive dep module.

* Change MacOS Clang std version to 20 from 2a

* Disable ranges on MacOS.
Remove CUDA testing - I just can't get CUDA to install any more.

* Update drone checkouts.

---------

Co-authored-by: Rene Rivera <grafikrobot@gmail.com>

test/Jamfile.v2

@@ -10,15 +10,20 @@
 
 import feature ;
 import testing ;
+import notfile ;
 
 project
     : requirements
       <toolset>gcc:<cxxflags>-Wno-deprecated-declarations
+      <library>/boost/core//boost_core
+      <library>/boost/detail//boost_detail
+      <library>/boost/type_traits//boost_type_traits
 ;
 
 
 import modules ;
-import ../checks/config : requires ;
+import-search /boost/config/checks ;
+import config : requires ;
 
 local is_unix = [ modules.peek : UNIX ] ;
 
@@ -98,7 +103,7 @@ test-suite config
           <threading>single
           <define>BOOST_DYN_LINK=1
           <define>BOOST_CONFIG_NO_LIB=1
-          <target-os>vxworks:<link>shared  
+          <target-os>vxworks:<link>shared
           :
           config_link_test
     ]

test/all/options_v2.jam

@@ -1,12 +1,12 @@
 # copyright John Maddock 2003
-# Use, modification and distribution are subject to the 
-# Boost Software License, Version 1.0. (See accompanying file 
+# Use, modification and distribution are subject to the
+# Boost Software License, Version 1.0. (See accompanying file
 # LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
 project
-    : requirements 
+    : requirements
      # threading tests require thread support turned on:
      <threading>multi
    ;
-   
-local test-requirements = <library>../../test/build//boost_test_exec_monitor  ;
+
+local test-requirements = <library>/boost/test//boost_test_exec_monitor  ;