Configure Searched Test Report Directories in the YAML

Add support for adding directories to search for Test Report XML files in the bitbucket-pipelines.yml. For example:

#!
pipelines:
  default:
    - step:
        test-reports:
          - ~/a/very/far/far/far/away/file/from/the/normal/scanner/*.xml
          - ~/**/different-name-to-default
        script:
          - echo "Hello"

As a follow up on Track Tests in Pipelines - Unit Tests.

For customers interested in this issue, can you please include your use-case for configuring this explicitly in the YAML. We're also curious if the build tool you are using supports reconfiguring the output directory of the test report generator.