text: Title: Support stopping execution using `robot:exit-on-failure` tag
  Body: The command line argument `--exitonfailure` has been very useful. If we can have a reserved tag `robot:exit-on-failure` that would be great so that the same behavior can be enabled in individual test suite. For example:
  
  `suite1.robot`:
  ```
  *** Settings ***
  Test Tags    robot:exit-on-failure
  
  *** Test Cases ***
  Pass
      Pass Execution    Pass this
  
  Scenario 1
      Simple Task 1
      Fail
      Simple Task 2     # Will not execute
  
  Scenario 2    # Will not execute
      Simple Task 1
      Fail
      Simple Task 2
  
  Scenario 3    # Will not execute
      Simple Task 1
      
  *** Keywords ***
  Simple Task 1
      Log To Console     ${\n}Simple Task 1...${\n}
  
  Simple Task 2
      Log To Console     ${\n}Simple Task 2...${\n}
  ```
  
  Output, something like this:
  ```
  ==============================================================================
  Suite1                                                                       
  ==============================================================================
  Suite1.Test                                                                  
  ==============================================================================
  Pass                                                                  | PASS |
  Pass this
  ------------------------------------------------------------------------------
  Scenario 1                                                            
  Simple Task 1...
  
  Scenario 1                                                            | FAIL |
  AssertionError
  ------------------------------------------------------------------------------
  Scenario 2                                                            | SKIP |
  Skipped due to exit-on-failure
  ------------------------------------------------------------------------------
  Scenario 3                                                            | SKIP |
  Skipped due to exit-on-failure
  ------------------------------------------------------------------------------
  Suite1.Test                                                           | FAIL |
  4 tests, 1 passed, 1 failed, 2 skipped
  ==============================================================================
  Suite1                                                                | FAIL |
  4 tests, 1 passed, 1 failed, 2 skipped
  ==============================================================================