[PkgConfigDeps] Creates *.pc files for build_requires and `test_r…

…equires` (#11390)

* Added test and build requires

* Moved tests to integration. Removed build_requires (not needed)

* from conan instead

conan/tools/gnu/pkgconfigdeps/pkgconfigdeps.py

@@ -11,8 +11,12 @@ def __init__(self, conanfile):
     def content(self):
         """Get all the *.pc files content"""
         pc_files = {}
+        # Get all the dependencies
         host_req = self._conanfile.dependencies.host
-        for _, dep in host_req.items():
+        test_req = self._conanfile.dependencies.test
+        for _, dep in list(host_req.items()) + list(test_req.items()):
+            # Require is not used at the moment, but its information could be used,
+            # and will be used in Conan 2.0
             dep_name = str(dep)
             for pc_name, pc_content in get_pc_files_and_content(self._conanfile, dep).items():
                 if pc_name in pc_files: