feat: Add NexusViewer

[rackstar]

Context

Closes #1166

Add NexusViewer to provide a unified view of system-wide data from various contracts within the Nexus Mutual platform

NOTE: this PR is behind #1164

Changes proposed in this pull request

• Add NexusViewer
• Add mocks
• Add fork tests
• Add unit tests

Test plan

• Add fork tests
• Add unit tests

Checklist

• Rebased the base branch
• Attached corresponding Github issue
• Prefixed the name with the type of change (i.e. feat, chore, test)
• Performed a self-review of my own code
• Followed the style guidelines of this project
• Made corresponding changes to the documentation
• Didn't generate new warnings
• Didn't generate failures on existing tests
• Added tests that prove my fix is effective or that my feature works

Review

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• 🍰 = Nice to have but not essential.
• 💡 = Suggestion or a comment based on personal opinion
• 🔨 = I believe this should be changed.
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• 🚀 = Feedback

[roxdanila]

See comments

[rackstar]

ready for review. but marking as DRAFT as it should not be merged until #1170 and #1164 are merged first

[roxdanila]

1. please stay consistent with naming the function argument: either manager or member across these functions
2. Slight scope creep: getManagerTokenRewards & getManagerRewards could be renamed to something a bit more descriptive: getManagerTokenRewardsByAddr, getManagerTokenRewardsByPoolIds,

[rackstar]

i'll change to getManagerTokenRewardsByAddr but we'll need to keep getManagerRewards to avoid a breaking change as its an existing method