Add docs for XcodeDeps improvements (#2619)

* add docs for improvements

* Update reference/conanfile/tools/apple.rst

Co-authored-by: Francisco Ramírez <franchuti688@gmail.com>

Co-authored-by: Luis Martinez <lasote@gmail.com>
Co-authored-by: Francisco Ramírez <franchuti688@gmail.com>

reference/conanfile/tools/apple.rst

@@ -66,36 +66,34 @@ case). The above commands generate the following files:
 
 .. code-block:: bash
 
-    .
-    ├── conan_libpng.xcconfig
-    ├── conan_libpng_debug_x86_64.xcconfig
-    ├── conan_libpng_release_x86_64.xcconfig
-    ├── conan_libpng_vars_debug_x86_64.xcconfig
-    ├── conan_libpng_vars_release_x86_64.xcconfig
-    ├── conan_zlib.xcconfig
-    ├── conan_zlib_debug_x86_64.xcconfig
-    ├── conan_zlib_release_x86_64.xcconfig
-    ├── conan_zlib_vars_debug_x86_64.xcconfig
-    ├── conan_zlib_vars_release_x86_64.xcconfig
-    ├── conandeps.xcconfig
-    └── conan_config.xcconfig
+  .
+  ├── conan_config.xcconfig
+  ├── conan_libpng.xcconfig
+  ├── conan_libpng_libpng.xcconfig
+  ├── conan_libpng_libpng_debug_x86_64.xcconfig
+  ├── conan_libpng_libpng_release_x86_64.xcconfig
+  ├── conan_zlib.xcconfig
+  ├── conan_zlib_zlib.xcconfig
+  ├── conan_zlib_zlib_debug_x86_64.xcconfig
+  ├── conan_zlib_zlib_release_x86_64.xcconfig
+  └── conandeps.xcconfig
 
 
 The first ``conan install`` with the default *Release* and *x86_64* configuration generates: 
 
-- *conan_libpng_vars_release_x86_64.xcconfig*: declares some intermediate variables that are included in *conan_libpng_release_x86_64.xcconfig*
-- *conan_libpng_release_x86_64.xcconfig*: includes *conan_libpng_vars_release_x86_64.xcconfig* and declares variables with conditional logic to be considered only for the active configuration in *Xcode* or the one passed by command line to *xcodebuild*.
-- *conan_libpng.xcconfig*: includes *conan_libpng_release_x86_64.xcconfig* and declares the following *Xcode* build settings: ``HEADER_SEARCH_PATHS``, ``GCC_PREPROCESSOR_DEFINITIONS``, ``OTHER_CFLAGS``, ``OTHER_CPLUSPLUSFLAGS``, ``FRAMEWORK_SEARCH_PATHS``, ``LIBRARY_SEARCH_PATHS``, ``OTHER_LDFLAGS``. It also includes the generated *xcconfig* files for transitive dependencies (*conan_zlib.xcconfig* in this case).
-- Same 3 files will be generated for each dependency in the graph. In this case, as *zlib* is a dependency of *libpng* it will generate: *conan_zlib_vars_release_x86_64.xcconfig*, *conan_zlib_release_x86_64.xcconfig* and *conan_zlib.xcconfig*.
+- *conan_libpng_libpng_release_x86_64.xcconfig*: declares variables with conditional logic to be considered only for the active configuration in *Xcode* or the one passed by command line to *xcodebuild*.
+- *conan_libpng_libpng.xcconfig*: includes *conan_libpng_libpng_release_x86_64.xcconfig* and declares the following *Xcode* build settings: ``HEADER_SEARCH_PATHS``, ``GCC_PREPROCESSOR_DEFINITIONS``, ``OTHER_CFLAGS``, ``OTHER_CPLUSPLUSFLAGS``, ``FRAMEWORK_SEARCH_PATHS``, ``LIBRARY_SEARCH_PATHS``, ``OTHER_LDFLAGS``. It also includes the generated *xcconfig* files for transitive dependencies (*conan_zlib_zlib.xcconfig* in this case).
+- *conan_libpng.xcconfig*: in this case it only includes *conan_libpng_libpng.xcconfig*, but in the case that the required package has components, this file will include all of the components of the package.
+- Same 3 files will be generated for each dependency in the graph. In this case, as *zlib* is a dependency of *libpng* it will generate: *conan_zlib_zlib_release_x86_64.xcconfig*, *conan_zlib_zlib.xcconfig* and *conan_zlib.xcconfig*.
 - *conandeps.xcconfig*: configuration files including all direct dependencies, in this case, it just includes ``conan_libpng.xcconfig``.
 - The main *conan_config.xcconfig* file, to be added to the project. Includes both the files from this generator and the generated by the :ref:`XcodeToolchain<conan_tools_apple_xcodetoolchain>` in case it was also set.
 
 The second ``conan install -s build_type=Debug`` generates: 
 
-- *conan_libpng_vars_debug_x86_64.xcconfig*: same variables as the one below for *Debug* configuration.
-- *conan_libpng_debug_x86_64.xcconfig*: same variables as the one below for *Debug* configuration.
-- *conan_libpng.xcconfig*: this file has been already creted by the previous command, now it's modified to add the include for *conan_libpng_debug_x86_64.xcconfig*.
-- Like in the previous command the same 3 files will be generated for each dependency in the graph. In this case, as *zlib* is a dependency of *libpng* it will generate: *conan_zlib_vars_debug_x86_64.xcconfig*, *conan_zlib_debug_x86_64.xcconfig* and *conan_zlib.xcconfig*.
+- *conan_libpng_libpng_debug_x86_64.xcconfig*: same variables as the one below for *Debug* configuration.
+- *conan_libpng_libpng.xcconfig*: this file has been already creted by the previous command, now it's modified to add the include for *conan_libpng_debug_x86_64.xcconfig*.
+- *conan_libpng.xcconfig*: this file will remain the same.
+- Like in the previous command the same 3 files will be generated for each dependency in the graph. In this case, as *zlib* is a dependency of *libpng* it will generate: *conan_zlib_zlib_debug_x86_64.xcconfig*, *conan_zlib_zlib.xcconfig* and *conan_zlib.xcconfig*.
 - *conandeps.xcconfig*: configuration files including all direct dependencies, in this case, it just includes ``conan_libpng.xcconfig``.
 - The main *conan_config.xcconfig* file, to be added to the project. Includes both the files from this generator and the generated by the :ref:`XcodeToolchain<conan_tools_apple_xcodetoolchain>` in case it was also set.