[jazzy] Bugfix for wrong timestamps in ros2 bag info (backport #1745)

[mergify]

• This PR addresses the incorrect display of the fractional part of the seconds in the ros2 bag info found in the Bug: Incorrect fractional part of seconds in output from the ros2 bag info #1744.

Correctly calculate the fractional part for seconds by subtracting nanoseconds_from_seconds from nanoseconds.

The changes covered by

rosbag2/rosbag2_tests/test/rosbag2_tests/test_rosbag2_info_end_to_end.cpp

Lines 41 to 61 in a85672f

	TEST_P(InfoEndToEndTestFixture, info_end_to_end_test) {
	internal::CaptureStdout();
	auto exit_code = execute_and_wait_until_completion("ros2 bag info cdr_test", bags_path_);
	std::string output = internal::GetCapturedStdout();
	auto expected_storage = GetParam();
	auto expected_file = rosbag2_test_common::bag_filename_for_storage_id("cdr_test_0", GetParam());
	std::string expected_ros_distro = "unknown";
	EXPECT_THAT(exit_code, Eq(EXIT_SUCCESS));
	// The bag size depends on the os and is not asserted, the time is asserted time zone independent
	EXPECT_THAT(
	output, ContainsRegex(
	"\nFiles: " + expected_file +
	"\nBag size: .*B"
	"\nStorage id: " + expected_storage +
	"\nROS Distro: " + expected_ros_distro +
	"\nDuration: 0.151137181s"
	"\nStart: Apr .+ 2020 .*:.*:36.763032325 \\(1586406456.763032325\\)"
	"\nEnd: Apr .+ 2020 .*:.*:36.914169506 \\(1586406456.914169506\\)"
	"\nMessages: 7"
	"\nTopic information: "));

• Relates Bug: Incorrect fractional part of seconds in output from the ros2 bag info #1744

  ---

  This is an automatic backport of pull request Bugfix for wrong timestamps in ros2 bag info #1745 done by Mergify.

[MichaelOrlov]

Pulls: #1752
Gist: https://gist.githubusercontent.com/MichaelOrlov/607a1d168b95c1d8fdb452ecffb0b81e/raw/74ca8da40f7e32fc8cc52305fa215f303535236d/ros2.repos
BUILD args: --packages-above-and-dependencies rosbag2_py rosbag2_tests
TEST args: --packages-above rosbag2_py rosbag2_tests
ROS Distro: jazzy
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/14262

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