Optimize Array to reduce Flow's Mtrie size and reduce number of reads

[fxamacker]

Issue To Be Solved

We can reduce memory use on Flow execution nodes.

See https://github.com/dapperlabs/flow-go/issues/6320

Suggested Solution

Optimize scalable Array to reduce memory use after completing #296.

Incorporate lessons learned during #296 (e.g. any unexpected issues found during Cadence integration) to avoid similar issues (if any) while optimizing scalable Array. If feasible, the solution should make changes to Cadence minimal (if any are required).

Updates #292
Updates onflow/flow-go#1744

[fxamacker]

Closed by #342