add support for numbers alignment in table output (#1202)

[cmanning09]

previously numbers alignment was hardcoded to 'right'. This change adds
the ability to set a configuration value 'numbers.align' in the
formatting section of the config to alter the format of the table output.

[danielmitterdorfer]

Thanks for your interest in Rally and your PR! We'll start the review process shortly.

@elasticmachine test this please

[DJRickyB]

Hi! Thank you for this. For the race subcommand things work as I would expect, but I wanted to note that when I use Rally's compare subcommand I get a failure, and it prints an error if the configuration is not defined:

[ERROR] Cannot compare. No value for mandatory configuration: section='reporting', key='numbers.align'

From the log:

Traceback (most recent call last):
  File "/Users/rick.boyd/dev/rally/esrally/config.py", line 178, in opts
    return self._opts[self._k(scope, section, key)]
KeyError: (<Scope.application: 1>, 'reporting', 'numbers.align')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/rick.boyd/dev/rally/esrally/rally.py", line 774, in dispatch_sub_command
    reporter.compare(cfg, args.baseline, args.contender)
  File "/Users/rick.boyd/dev/rally/esrally/reporter.py", line 48, in compare
    ComparisonReporter(cfg).report(
  File "/Users/rick.boyd/dev/rally/esrally/reporter.py", line 315, in __init__
    self.numbers_align = config.opts("reporting", "numbers.align")
  File "/Users/rick.boyd/dev/rally/esrally/config.py", line 183, in opts
    raise exceptions.ConfigError(f"No value for mandatory configuration: section='{section}', key='{key}'")
esrally.exceptions.ConfigError: No value for mandatory configuration: section='reporting', key='numbers.align'

[cmanning09]

Good catch. I have addressed the issue you raised. Please let me know if there is anything else.

[DJRickyB]

wonderful! thank you @cmanning09. This code functions as I'd expect, and as you indicated in the initial commit it addresses #1202 nicely.

I have one more ask/iteration of you: this functionality should be documented. please consider whether it will be supported similarly to the reporting.format key, in that it's only documented as the CLI --report-format flag (in which case more code would be required), or if users should always specify it in the [reporting] section of their local .ini. Note that the documentation for that section states This section defines how metrics are stored. and so would need to be updated for the new meaning.

Thank you!

[cmanning09]

I addressed your concern by adding support through CLI flags for both race and compare subcommands. Is there anything else?

[DJRickyB]

Beautiful! I've tested it and it works as expected. Please add the documentation and then I think we're all set. (Should be in docs/command_line_reference.rst)

[DJRickyB]

Thank you!

[DJRickyB]

@elasticmachine run tests

[DJRickyB]

@cmanning09, just as an update: I am having trouble getting this branch to pass our internal CI. I don't believe this is due to your code, so please bear with me. Once tests pass cleanly I will merge this one in

[DJRickyB]

@elasticmachine update branch

[DJRickyB]

@elasticmachine run tests