Forward NewBlock events to all workers to clear pending packets if needed

[romac]

This is best reviewed one commit after the other.

Description

• Forward NewBlock events to all workers to clear pending packets if needed.
• Document the code in supervisor.rs

Tested by following the instructions in https://hermes.informal.systems/tutorial_relay_existing_path.html.

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For contributor use:

• Updated the Unreleased section of CHANGELOG.md with the issue.
• If applicable: Unit tests written, added test to CI.
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Updated relevant documentation (docs/) and code comments.
• Re-reviewed Files changed in the Github PR explorer.

[codecov-io]

Codecov Report

Merging #733 (bc0ecc5) into master (b1b37f5) will increase coverage by 30.4%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #733      +/-   ##
=========================================
+ Coverage    13.6%   44.1%   +30.4%     
=========================================
  Files          69     156      +87     
  Lines        3752   10356    +6604     
  Branches     1374       0    -1374     
=========================================
+ Hits          513    4572    +4059     
- Misses       2618    5784    +3166     
+ Partials      621       0     -621     

Impacted Files	Coverage Δ
...application/ics20_fungible_token_transfer/error.rs	0.0% <ø> (ø)
...ion/ics20_fungible_token_transfer/msgs/transfer.rs	0.0% <ø> (ø)
..._transfer/relay_application_logic/send_transfer.rs	0.0% <ø> (ø)
modules/src/events.rs	0.0% <ø> (ø)
modules/src/handler.rs	100.0% <ø> (ø)
modules/src/ics02_client/client_def.rs	47.3% <ø> (ø)
modules/src/ics02_client/client_type.rs	79.1% <ø> (+31.5%)	⬆️
modules/src/ics02_client/context.rs	100.0% <ø> (ø)
modules/src/ics02_client/error.rs	100.0% <ø> (ø)
modules/src/ics02_client/events.rs	15.7% <ø> (+15.7%)	⬆️
... and 259 more

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[ancazamfir]

Cool stuff! As we discussed the spawning of workers from chain state scanning will be done in a different PR. Thanks Romain!