qa: Consider cache and config.ini relative to invocation directory

In CMake-based build system (1) `config.ini` is created in the build
directory, and (2) `cache` must also be created in the same directory.

This change enables running individual functional tests from the build
directory.

test/functional/test_framework/test_framework.py

@@ -103,7 +103,7 @@ def __init__(self, test_file) -> None:
         self.rpc_timeout = 60  # Wait for up to 60 seconds for the RPC server to respond
         self.supports_cli = True
         self.bind_to_localhost_only = True
-        self.parse_args()
+        self.parse_args(test_file)
         self.default_wallet_name = "default_wallet" if self.options.descriptors else ""
         self.wallet_data_filename = "wallet.dat"
         # Optional list of wallet names that can be set in set_test_params to
@@ -155,14 +155,14 @@ def main(self):
             exit_code = self.shutdown()
             sys.exit(exit_code)
 
-    def parse_args(self):
+    def parse_args(self, test_file):
         previous_releases_path = os.getenv("PREVIOUS_RELEASES_DIR") or os.getcwd() + "/releases"
         parser = argparse.ArgumentParser(usage="%(prog)s [options]")
         parser.add_argument("--nocleanup", dest="nocleanup", default=False, action="store_true",
                             help="Leave bitcoinds and test.* datadir on exit or error")
         parser.add_argument("--noshutdown", dest="noshutdown", default=False, action="store_true",
                             help="Don't stop bitcoinds after the test execution")
-        parser.add_argument("--cachedir", dest="cachedir", default=os.path.abspath(os.path.dirname(os.path.realpath(__file__)) + "/../../cache"),
+        parser.add_argument("--cachedir", dest="cachedir", default=os.path.abspath(os.path.dirname(test_file) + "/../cache"),
                             help="Directory for caching pregenerated datadirs (default: %(default)s)")
         parser.add_argument("--tmpdir", dest="tmpdir", help="Root directory for datadirs (must not exist)")
         parser.add_argument("-l", "--loglevel", dest="loglevel", default="INFO",
@@ -177,7 +177,7 @@ def parse_args(self):
         parser.add_argument("--coveragedir", dest="coveragedir",
                             help="Write tested RPC commands into this directory")
         parser.add_argument("--configfile", dest="configfile",
-                            default=os.path.abspath(os.path.dirname(os.path.realpath(__file__)) + "/../../config.ini"),
+                            default=os.path.abspath(os.path.dirname(test_file) + "/../config.ini"),
                             help="Location of the test framework config file (default: %(default)s)")
         parser.add_argument("--pdbonfailure", dest="pdbonfailure", default=False, action="store_true",
                             help="Attach a python debugger if test fails")