[Protocol] Add a `NumBlocksPerSession` governance parameter

[Olshansk]

Objective

Implementation of NumBlocksPerSessionwithout hacky tech debt.

Origin Document

There are many comments and temporary workaround in the code. the following is just one of them:

const (
    // TODO_BLOCKER: Remove direct usage of these constants in helper functions
    // when they will be replaced by governance params
    NumBlocksPerSession = 4

Goals

• Resolve a lot of TECHDEBT related to the number of blocks per session
• Implement some of the core macro utility of the protocol

Deliverables

Reminder: This can be multiple PRs

• [x] Add governance parameters for sessionkeeper.NumBlocksPerSession (#530)
• [x] Techdebt - search for, identify, update and cleanup all comments / code / functions related to documented tech debt.

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• [x] Business logic - implement the actual thing
• [ ] Testing
  • [x] Ensure we have at least 1 E2E test
  • [ ] Ensure we have at least 1 integration (in memory) test
• [ ] Makefile targets to:
  • [x] Modify / update the parameters
  • [x] Run the relevant E2E tests
• [ ] Docs in docusurus to to minimally document this new parameter

Non-goals / Non-deliverables

• Exhaustively testing all edge cases and variations of changing this value

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Creator: @Olshansk Co-Owners: @bryanchriswhite