Dividends page fixes

[monitz87]

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• I've added this PR's link to its Asana task(s)
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This PR:

• Hides the checkpoint creation button if the dividends module hasn't been enabled
• Fixes the checkpoint fetching SDK function (was throwing an error because of web3 documentation nonsense)
• Reorders the checkpoint caching/creation logic in the state
• Replaces hardcoded security token symbol with router param in the checkpoint list
• Fixes the bug that caused the transaction modal to not disappear after enabling the dividends module
• Renames Checkpoints to CheckpointList and Checkpoint to DividendList
• Passes the downloadOwnershipList container function to the CheckpointList presenter and calls it when the button is clicked