Add helper functions for slot time deadlines

[0xYYY]

This PR adds some helper functions to phase0 for getting deadlines of various slot components.

Related PR: #4542

Fixes #4586

[0xYYY]

TODO (create the following helper functions and update spec/tests to use these instead of get_slot_component_duration_ms):

• get_proposer_reorg_cutoff_ms
• get_attestation_due_ms
• get_aggregate_due_ms
• get_sync_message_due_ms
• get_contribution_due_ms
• get_payload_attestation_due_ms
• get_view_freeze_cutoff_ms
• get_inclusion_list_submission_due_ms
• get_proposer_inclusion_list_cutoff_ms

hi @jtraglia, creating this initial draft with one of the functions
would like to get some feedback, and if all is good, will proceed to implement changes for rest of the functions

[jtraglia]

@0xYYY Yes, this look good. Please continue!

[0xYYY]

hi @jtraglia, thanks for the comments
i have also made the changes for other functions, and the PR is ready to be reviewed now

[jtraglia]

Really great work @0xYYY, thank you!

I would like for @dankrad & @rolfyone to review this too.

[rolfyone]

LGTM

[dankrad]

Looks great :)

[nflaig]

this returns 3999 for the attestation deadline

>>> 3333 * 12000 // 10000
3999

wondering if we rather wanna round to closest integer to have cleaner values

[jtraglia]

This came up in the original PR too. We could do something like this if devs want it.

• Replace INTERVALS_PER_SLOT with explicit slot component times #4476 (comment)

[nflaig]

Ah I missed that comment, I guess there isn't a need to adapt it on the spec, can just change the rounding in our code eg. can just use Math.round instead of Math.floor, the difference is negligible so it shouldn't matter either way.