Fixing bug in average time remaining calculation in present value

[slundqui]

Resolved Issues

• State generation for long_average_maturity_time and short_average_maturity_time in tests do not cover full range of possible values, due to the underlying fields in pool info being scaled by 1e18.
• Fixing time remaining calculation in calculate_present_value to account for average maturity time being scaled.

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[[Reviewer Name]]

Rust

• Testing
  • Are there new or updated unit or integration tests?
  • Do the tests cover the happy paths?
  • Do the tests cover the unhappy paths?
  • Are there an adequate number of fuzz tests to ensure that we are
    covering the full input space?
  • If matching Solidity behavior, are there differential fuzz tests that
    ensure that Rust matches Solidity?