Fix CMake build detection of libaec

Partial revert of #4567 as libaec
is the correct name of the package and should be searched first.

Also fixes pkg-config generation handling. This does mean the output
CMake configuration files need to `find_package(libaec)` prior to
`hdf5-static`, but it also avoids using absolute path to shared library
so that users can do `set(libaec_USE_STATIC_LIBS ON)`.

CMakeFilters.cmake

@@ -160,15 +160,27 @@ if (HDF5_ENABLE_SZIP_SUPPORT)
     endif ()
     set(libaec_USE_STATIC_LIBS ${HDF5_USE_LIBAEC_STATIC})
     set(SZIP_FOUND FALSE)
-    find_package (SZIP NAMES ${LIBAEC_PACKAGE_NAME}${HDF_PACKAGE_EXT} COMPONENTS ${LIBAEC_SEACH_TYPE})
+    find_package (libaec CONFIG)
     if (NOT SZIP_FOUND)
-      find_package (SZIP) # Legacy find
+      find_package (SZIP NAMES ${LIBAEC_PACKAGE_NAME}${HDF_PACKAGE_EXT} COMPONENTS ${LIBAEC_SEACH_TYPE}) # Legacy find
+      if (NOT SZIP_FOUND)
+        find_package (SZIP) # Legacy find
+      endif ()
     endif ()
     set(H5_SZIP_FOUND ${SZIP_FOUND})
     if (H5_SZIP_FOUND)
       set (H5_SZIP_INCLUDE_DIR_GEN ${SZIP_INCLUDE_DIR})
       set (H5_SZIP_INCLUDE_DIRS ${H5_SZIP_INCLUDE_DIRS} ${SZIP_INCLUDE_DIR})
-      set (LINK_COMP_LIBS ${LINK_COMP_LIBS} ${SZIP_LIBRARIES})
+      if (TARGET libaec::sz)
+        # The libaec-config.cmake does not set an OUTPUT_NAME
+        # on the target. The target returned is: libaec::sz
+        get_filename_component (libname ${SZIP_LIBRARIES} NAME_WLE)
+        string (REGEX REPLACE "^lib" "" libname ${libname})
+        set_target_properties (libaec::sz PROPERTIES OUTPUT_NAME ${libname})
+        set (LINK_COMP_LIBS ${LINK_COMP_LIBS} libaec::sz)
+      else ()
+        set (LINK_COMP_LIBS ${LINK_COMP_LIBS} ${SZIP_LIBRARIES})
+      endif ()
     endif ()
   else ()
     if (HDF5_ALLOW_EXTERNAL_SUPPORT MATCHES "GIT" OR HDF5_ALLOW_EXTERNAL_SUPPORT MATCHES "TGZ")