Add slow tests issues report

What does this MR do and why?

Related gitlab-org/gitlab#387973 (closed)

Example of issue created gitlab-org-sandbox/rails-test-failures#24 (closed)

Describe in detail what your merge request does and why.

Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

files = ['/Users/alinamihaila/Documents/work/rspec-test-reports/rspec-4509805924.json']
token = "token"

report = GitlabQuality::TestTooling::Report::SlowTestIssue.new(token: token, input_files: files, project: "46635874")

report.invoke!

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.