…tation` value

Previously: `excluded_tests` excluded selections
that have the same values for the fields included in `selection_pattern`.

However, as `selection_pattern` doesn't contain `expectation`,
`expectation` can't be used in `excluded_tests`, blocking [1].

After this CL: `excluded_tests` excluded selections
that have the same values for all the fields (except for `name`).

For this purpose, this CL:

- Sets `delivery_key` for `excluded_selection`, so that
  selections and excluded selections have the same set of fields.
- Uses `dump_test_parameters()` rather than `selection_pattern`
  for exclusion matching (`exclusion_dict`).
- Applies exclusions after all overrides are processed.
  This is a fix for cases like:
  - "default" selection A
  - "override" selection B, overriding A
  - exclusion pattern E, matching B but not A
  Previously: E excludes B but not A, so A is generated.
  After this CL: B overrides A, then E excludes B.
    As A is already overridden, no selections are generated.

This CL doesn't change generated results, because before [1]
there are no cases hitting these issues.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/1991066

Bug: 906850
Change-Id: Ifa36167df710edd89d4e572346a3f1b928710119
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1991074
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#731904}