Replace `INTERVALS_PER_SLOT` with explicit slot component times

[eserilev]

Issue Addressed

https://github.com/ethereum/consensus-specs/pull/4476

Additional Info

This change affects many critical paths in lighthouse and should not be merged until after 8.0.0

the Ethereum kurtosis package is working to support this change here: https://github.com/ethpandaops/ethereum-package/pull/1168

[dapplion]

Should this change consider that the slot time will change in the future? Or that's to be handled in a future PR

[eserilev]

Should this change consider that the slot time will change in the future? Or that's to be handled in a future PR

I think we should handle that in a future PR to keep this diff here as small as possible

[mergify[bot]]

This pull request has merge conflicts. Could you please resolve them @eserilev? 🙏

[jimmygchen]

🤖 General question: Are there plans to deprecate seconds_per_slot? Both fields now exist in ChainSpec. Should seconds_per_slot be marked deprecated or documented as maintained only for config backward compatibility?

[jimmygchen]

🤖 There's a stale comment reference in beacon_node/network/src/network_beacon_processor/sync_methods.rs:302 that mentions slot_clock.single_lookup_delay() which was removed in this PR. Should update or remove this reference.

[eserilev]

Fixed the above comments

[jimmygchen]

Thanks for addressing the feedback! The fixes look good

[mergify[bot]]

This pull request has merge conflicts. Could you please resolve them @eserilev? 🙏