Add support for multi-platform bundle generation and additional files/certs

[nicolaswill]

Custom bundle creation now uses a platform-independent CodeQL base bundle and creates separate output bundles for Windows, Linux, and MacOS. These bundles are exposed via the QLT_CODEQL_BUNDLE_PATH_WIN64, QLT_CODEQL_BUNDLE_PATH_LINUX64, and QLT_CODEQL_BUNDLE_PATH_OSX64 environment variables, with QLT_CODEQL_BUNDLE_PATH continuing to map to the bundle compatible with the runner platform.

Additional files/directories or certificates can now be specified in qlt.conf.json with the following schema:

        schema = {
            "type": "object",
            "properties": {
                "CodeQLBundleAdditionalFiles": {
                    "type": "array",
                    "items": {
                        "type": "object",
                        "properties": {
                            "Source": {"type": "string"},
                            "Destination": {"type": "string"},
                        },
                        "required": ["Source", "Destination"],
                        "additionalProperties": False,
                    },
                    "minItems": 1,
                },
                "CodeQLBundleAdditionalCertificates": {
                    "type": "array",
                    "items": {
                        "type": "object",
                        "properties": {"Source": {"type": "string"}},
                        "required": ["Source"],
                        "additionalProperties": False,
                    },
                    "minItems": 1,
                },
            },
            "additionalProperties": True,
        }