feat(cmakev2/project): move all project-related items into project.cmake

The current approach involves transparently calling __init_build within
idf_build_library and performing all post-project() initialization
there. The issue with this method is that project_include.cmake files
also need to be included during post-project() initialization, but they
should be included in the global scope. This cannot be achieved within
the __init_build function unless it is converted into a macro. Although
using a macro is a potential solution, it risks causing global scope
pollution. Another complication is the location where project() can be
invoked; it must be explicitly[1] stated in the project's
CMakeLists.txt.  This requirement conflicts with our intention to wrap
it within the idf_project_default helper. Given these challenges, it
makes sense to introduce an explicit idf_project_init macro, where all
post-project() initialization occurs, including the inclusion of
project_include.cmake files. While we can still encapsulate this within
idf_project_default, for the plumbing commands (idf_build_library,
idf_build_executable, ...), it will need to be explicitly called after
the project() invocation.

Usage for default project:

cmake_minimum_required(VERSION 3.22)
include($ENV{IDF_PATH}/tools/cmakev2/idf.cmake)
project()
idf_project_default()

Usage for plumbing commands:

cmake_minimum_required(VERSION 3.22)
include($ENV{IDF_PATH}/tools/cmakev2/idf.cmake)
project()
idf_project_init()
idf_build_library()
...

[1] https://cmake.org/cmake/help/latest/command/project.html#usage

Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>

tools/cmakev2/test/CMakeLists.txt

@@ -11,6 +11,8 @@ project(cmakev2
     VERSION 1.2.3
     LANGUAGES C CXX ASM)
 
+idf_project_init()
+
 # Test component priority
 function(test_component_priority)
     # Set the idf component to be replaced with a testing component of higher