try to bring down the length of symbols a bit (#1498)

Author: ericniebler

include/exec/__detail/__system_context_default_impl.hpp

@@ -16,10 +16,11 @@
 #pragma once
 
 #include "__system_context_replaceability_api.hpp"
-#include "stdexec/execution.hpp"
-#include "exec/static_thread_pool.hpp"
+
+#include "../../stdexec/execution.hpp"
+#include "../static_thread_pool.hpp"
 #if STDEXEC_ENABLE_LIBDISPATCH
-#  include "exec/libdispatch_queue.hpp"
+#  include "../libdispatch_queue.hpp" // IWYU pragma: keep
 #endif
 
 #include <atomic>

include/exec/__detail/__system_context_replaceability_api.hpp

@@ -17,7 +17,7 @@
 #ifndef STDEXEC_SYSTEM_CONTEXT_REPLACEABILITY_API_H
 #define STDEXEC_SYSTEM_CONTEXT_REPLACEABILITY_API_H
 
-#include "stdexec/__detail/__execution_fwd.hpp"
+#include "../../stdexec/__detail/__execution_fwd.hpp"
 
 #include <cstdint>
 #include <cstddef>

include/exec/libdispatch_queue.hpp

@@ -27,7 +27,7 @@
 #    define __has_extension(x) false
 #  endif
 
-#  include "stdexec/execution.hpp"
+#  include "../stdexec/execution.hpp"
 #  include <dispatch/dispatch.h>
 
 namespace exec {

include/exec/start_now.hpp

@@ -15,13 +15,13 @@
  */
 #pragma once
 
-#include "stdexec/__detail/__execution_fwd.hpp"
+#include "../stdexec/__detail/__execution_fwd.hpp"
 
-#include "stdexec/__detail/__concepts.hpp"
-#include "stdexec/__detail/__env.hpp"
-#include "stdexec/__detail/__receivers.hpp"
-#include "stdexec/__detail/__senders.hpp"
-#include "stdexec/__detail/__meta.hpp"
+#include "../stdexec/__detail/__concepts.hpp"
+#include "../stdexec/__detail/__env.hpp"
+#include "../stdexec/__detail/__receivers.hpp"
+#include "../stdexec/__detail/__senders.hpp"
+#include "../stdexec/__detail/__meta.hpp"
 
 #include "async_scope.hpp"
 

include/exec/system_context.hpp

@@ -17,7 +17,7 @@
 
 #include <utility>
 
-#include "stdexec/execution.hpp"
+#include "../stdexec/execution.hpp"
 #include "__detail/__system_context_replaceability_api.hpp"
 
 #ifndef STDEXEC_SYSTEM_CONTEXT_SCHEDULE_OP_SIZE