chore: audit epoch (backport #24610)

[mergify]

addresses OS-CDK-ADV-01

Summary by CodeRabbit

• Bug Fixes
  • Improved accuracy in epoch handling by ensuring epochs do not start prematurely and by preventing block calculations before an epoch begins.
• Documentation
  • Updated documentation to accurately describe the genesis state function for epochs.
• Chores
  • Removed an unused constant related to default indexing.
• Tests
  • Adjusted test expectations to reflect corrected epoch start behavior and improved test organization.

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This is an automatic backport of pull request #24610 done by [Mergify](https://mergify.com).

[ironbird-prod]

Ironbird - launch a network

To use Ironbird, you can use the following commands:

• /ironbird start OR /ironbird start --load-test-config= - Launch a testnet with the specified chain and load test configuration.
• /ironbird chains - List of chain images that ironbird can use to spin-up testnet
• /ironbird loadtests - List of load test modes that ironbird can run against testnet

Custom Load Test Configuration

You can provide a custom load test configuration using the `--load-test-config=` flag:

/ironbird start cosmos --load-test-config={
  "block_gas_limit_target": 0.75,
  "num_of_blocks": 50,
  "msgs": [
    {"weight": 0.3, "type": "MsgSend"},
    {"weight": 0.3, "type": "MsgMultiSend"},
	{"weight": 0.4, "type": "MsgArr", "ContainedType": "MsgSend", "NumMsgs": 3300}
  ]
}

Use /ironbird loadtests to see more examples.