tweak format of test failures

Dependencies

• [2] CZQ3NJ4N Merge text0
• [3] ARYMNK52 merge bugfix: show test failures
• [4] ZKH2N6MN Merge text0
• [5] ORRSP7FV deduce test names on failures
• [6] AVTNUQYR basic test-enabled framework
• [7] 36Z442IV back to commit 8123959e52f without code editing
• [*] 3QNOKBFM beginnings of a test harness

Change contents

• replacement in app.lua at line 75
  [3.61]→[3.61:131](∅→∅)
  − error('There were test failures:\n\n'..table.concat(Test_errors))
  [3.61]

  [3.131]
  + error('There were test failures:\n\n'..table.concat(Test_errors, '\n'))
• replacement in app.lua at line 453
  [4.60966]→[4.60966:61148](∅→∅)
  − local file_and_line_number = stack_trace:gsub('stack traceback:\n', ''):gsub(': .*', '')

  − local full_error = file_and_line_number..':'..test_name..' -- '..err_without_line_number
  [4.60966]

  [4.61148]
  + local file_and_line_number = stack_trace:gsub('stack traceback:\n', ''):gsub(': .*', '') --[[strip newline and tab]] :sub(3)

  + local full_error = test_name..' -- '..file_and_line_number..' '..err_without_line_number