fix: waiting for proposal in pre-commit phase

[b00f]

Description

This pull request addresses a situation observed in the Testnet where certain nodes with slow connections become absentees in the certificate. This occurs when they receive block announcements before entering the pre-commit phase, possibly due to late proposals or votes.

To address this issue, the following changes have been made:

• When there are sufficient pre-commit votes but no proposal, the system now waits to receive the proposal before proceeding.
• If a proposal is received after committing a block, it is now accepted.
• If timeout expires in pre-commit phase, we move to the change-proposer phase.

These scenarios are covered by tests, and also been tested using TLA+ to ensure its correctness.

[codecov]

Codecov Report

Merging #486 (060a2c8) into main (24442b8) will decrease coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #486      +/-   ##
==========================================
- Coverage   82.44%   82.37%   -0.07%     
==========================================
  Files         150      150              
  Lines        7059     7071      +12     
==========================================
+ Hits         5820     5825       +5     
- Misses        945      953       +8     
+ Partials      294      293       -1