Add support for test_suffixes in --tests args

[jdstanko]

This adds filtering tests with suffixes when using run_suite_class. The behavior when using run_suite, is not modified as that function does not currently support using name_suffix when running tests.

The expected form of the --tests CLI arg is <test_class_name>[_<test_suffix>][.<test_name>] e.g. Foo_A.bar would run the A configuration of test bar on test class Foo

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This change is 

[xianyuanjia]

Reviewable status: 0 of 3 files reviewed, 3 unresolved discussions (waiting on @jdstanko and @mhaoli)

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mobly/suite_runner.py line 119 at r1 (raw file):

      metavar='[ClassA[.test_a] ClassB[.test_b] ...]',
      help='A list of test classes and optional tests to execute.',
  )

Should also update the CLI usage here

Also point out limitations of using suffix

Code quote:

  parser.add_argument(
      '--tests',
      '--test_case',
      nargs='+',
      type=str,
      metavar='[ClassA[.test_a] ClassB[.test_b] ...]',
      help='A list of test classes and optional tests to execute.',
  )

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mobly/suite_runner.py line 399 at r1 (raw file):

  # The user is selecting some tests to run. Parse the selectors.
  # Dict from test_name class name to list of tests to execute (or None for all
  # tests).

technically the output here would be dict from tuple to list of tests. Either update or drop the comment

Code quote:

  # Dict from test_name class name to list of tests to execute (or None for all
  # tests).

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mobly/suite_runner.py line 421 at r1 (raw file):

  This function transforms a list of selector strings (such as FooTest or
  FooTest.test_method_a) to a dict where keys are test_name classes, and

The "keys" here in the docstring should also be updated

[jdstanko]

Reviewable status: 0 of 3 files reviewed, 3 unresolved discussions (waiting on @mhaoli and @xianyuanjia)

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mobly/suite_runner.py line 119 at r1 (raw file):

Previously, xianyuanjia wrote…

Should also update the CLI usage here

Also point out limitations of using suffix

Done.

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mobly/suite_runner.py line 399 at r1 (raw file):

Previously, xianyuanjia wrote…

technically the output here would be dict from tuple to list of tests. Either update or drop the comment

Done.

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mobly/suite_runner.py line 421 at r1 (raw file):

Previously, xianyuanjia wrote…

The "keys" here in the docstring should also be updated

Done.

[xianyuanjia]

Reviewable status: 0 of 3 files reviewed, all discussions resolved (waiting on @mhaoli)