Improve section Logging Monitoring Data

See merge request !2

Improve the wording for this section.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

Apply fixes and improvements for first review

See merge request !1

This commit fixes some typos and improves the Logging Monitoring Data
section to explain why the wrapper script example uses the stderr to
fetch the resources monitoring information.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

README: Add a high level introduction

See merge request araujo/lava-tests-monitoring!1

Set expectations before diving in the technical details.

This commit adds a test example setting an optional limit to the
maximum_resident_set_size metrics value, and if the test goes beyond it,
it shows the test result as failed.

It also updates the README explaining in more detail the wrapper script
design and the available examples in this repository.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

This commit adds the new section `Logging Monitoring Data` which
explains the approach to capture metrics during the test execution.

It also adds the `Test Measurement Results` section explaining how to
check for the metrics values in LAVA.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>