feat(consensus): connect to all other quorum members

[lklimek]

Issue being fixed or feature implemented

Time between generation of a proposal and delivery to last validator is too high. To improve this, we can establish direct connections between all validators in the quorum.

What was done?

Implemented validator connection selector allValidatorsSelector that selects all validators in the quorum except self.

Introduced new config option:

[consensus]
# ValidatorConnectionAlgorithm defines the algorithm used to select the
# validators to which direct connection should be established.
# Possible values are:
# - "all" - validators establish direct connections to all other validators in the current quorum
# - "dip6" - validators establish direct connections to a subset of other validators, determined according to DIP-6
#
# Defaults to "dip6".
validator-connection-algorithm = "{{ .Consensus.ValidatorConnectionAlgorithm }}"

How Has This Been Tested?

NOT TESTED YET

Breaking Changes

None - backwards-compatible

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone