For some reason the error message from flutter SDK might contain no useful information. Basically it just says that test failed and you should see the logs. Logs itself are provided as content of `print` event. This commit adds special processing for this behavior - it parses actual error message out of print event.

Improve test error messages from flutter

Report will contain less accurate information but it will be easier to read.

Previously we listed tests using markdown tables. Each test group had it's own table and textual preface saying how many tests were executed in what time.
This was completely reworked - now tests are listed inside code block. Grouping is achieved using simple indentation. Duration of individual tests is no longer shown - it produced too much "noise" in the report. Pass/Fail check-mark was also moved before name of test suite.
Behavior of "listTests" option was also changed - now if set to failed, it will list all tests, but only if suite is failed. Otherwise test listing is completely omitted.
Last change affects report trimming - if report is still too big after "listTests" is set to "failed" - it will trim report to fit max size and add informational message at the end.

Improve report

GitHub UI for some unknown reason navigates user to check run with `check_suite_focus=true` query argument. With this argument unfortunately navigation to document ID with `#something` doesn't work

Adds full URL in place previous commit missed

Use full URL to link test suites

Add support for mocha-json