Wait to vote until the end of the proposal period

[evan-forbes]

As a simple mechanism to implement consistent block (and commitment!) times, it has been suggested that we should simply wait to count non-nil prevotes until the end of the proposal period.

AC

• Wait to count non-nil votes until the end of the proposal period
• Test for consistent block times even with variable loads

[staheri14]

While prototyping this new method, I want to note some questions that come to mind to ensure we address them in the final implementation (will keep editing this comment with my other questions):

1. Does this modification require any adjustment to the transaction's TTL?