Ord on signed entity type discriminants

[Alenar]

Content

This PR enforce an order implementation for the signed entity type discriminant.

The order is defined as the following:

MithrilStakeDistribution < CardanoStakeDistribution < CardanoImmutableFilesFull < CardanoTransactions

This order was already correctly implement using a simple derive Ord with the work on #1496 (to allow the capabilities field of the aggregator root endpoint to use a BTreeSet).

This PR:

• add tests to ensure that the defined order is the one defined above doesn't change by mistake by, for example, reordering the signed entity enum variants.
• change aggregator Configuration::list_allowed_signed_entity_types_discriminants return type to a BTreeSet for automatic order based on the type and automatic de-duplication. This simplify a bit the open message generation order (that's ultimately based on this method).

Pre-submit checklist

• Branch
  • [x] Tests are provided (if possible)
  • [x] Crates versions are updated (if relevant)
  • [x] Commit sequence broadly makes sense
  • [x] Key commits have useful messages
• PR
  • [x] No clippy warnings in the CI
  • [x] Self-reviewed the diff
  • [x] Useful pull request description
  • [x] Reviewer requested

Issue(s)

Closes #1648

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Test Results

    3 files  ±0     43 suites  ±0   8m 23s :stopwatch: -15s   978 tests +2    978 :white_check_mark: +2  0 :zzz: ±0  0 :x: ±0  1 072 runs  +2  1 072 :white_check_mark: +2  0 :zzz: ±0  0 :x: ±0 

Results for commit 3f3fb02d. ± Comparison against base commit f36ddb23.

:recycle: This comment has been updated with latest results.