PAX: make cmake_minimum_required() check at top

When building PAX:

```
make -j$(nproc) -C ~/cloudberry
```

Will have a warning as the follows:

```
 build pax, USE_MANIFEST_API=OFF USE_PAX_CATALOG=ON
 CMake Warning (dev) at CMakeLists.txt:1 (project):
   cmake_minimum_required() should be called prior to this top-level project()
   call.  Please see the cmake-commands(7) manual for usage documentation of
   both commands.
 This warning is for project developers.  Use -Wno-dev to suppress it.
```

This change is to let the building run without warning, or else can
cause a little confusion for users and developers.

Author: tuhaihe

contrib/pax_storage/CMakeLists.txt

@@ -1,5 +1,5 @@
-project(Pax)
 cmake_minimum_required (VERSION 3.11.0)
+project(Pax)
 set(CMAKE_CXX_STANDARD 17)
 
 set(TOP_DIR ${PROJECT_SOURCE_DIR}/../..)