chore: update Eclipse validator sets to include Stride, minor cleanup (…

…#4747)

### Description

- deletes all the mainnet2 artifacts that we don't need
- moves the sealevel helper scripts into more explicit directories, and
ensures thresholds are appropriate
- updates the eclipse ISM

### Drive-by changes

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### Related issues

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- Fixes #[issue number here]
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### Backward compatibility

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### Testing

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