[move] add const accessors to AccountAddress

[conr2d]

Description

This PR adds const qualifier to accessors to AccountAddress inner data and a const constructor from u64.

How Has This Been Tested?

Added test case.

Key Areas to Review

This PR doesn't add non-trivial changes that can break existing code.

Type of Change

• New feature
• Bug fix
• Breaking change
• Performance improvement
• Refactoring
• Dependency update
• Documentation update
• Tests

Which Components or Systems Does This Change Impact?

• Validator Node
• Full Node (API, Indexer, etc.)
• Move/Aptos Virtual Machine
• Aptos Framework
• Aptos CLI/SDK
• Developer Infrastructure
• Move Compiler
• Other (specify)

Checklist

• I have read and followed the CONTRIBUTING doc
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I identified and added all stakeholders and component owners affected by this change as reviewers
• I tested both happy and unhappy path of the functionality
• I have made corresponding changes to the documentation

[trunk-io]

⏱️ 7s total CI duration on this PR

Job	Cumulative Duration	Recent Runs
permission-check	4s	🟥
permission-check	3s	🟥

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[github-actions]

This issue is stale because it has been open 45 days with no activity. Remove the stale label, comment or push a commit - otherwise this will be closed in 15 days.

[github-actions]

This issue is stale because it has been open 45 days with no activity. Remove the stale label, comment or push a commit - otherwise this will be closed in 15 days.

[github-actions]

This issue is stale because it has been open 45 days with no activity. Remove the stale label, comment or push a commit - otherwise this will be closed in 15 days.