docs(specs): restructure zones spec (#377)

* docs: create zone spec scaffolding

* wip: split proving system and batch submission

* docs: abstract

* docs: update abstract

* docs: remove motivation section

* docs: terminology

* docs: remove params

* docs: system overview

* docs: zone deployment

* fmt: spacing

* docs: deposits

* docs: deposit queue, fees

* docs: encrypted deposits

* docs: encrypted deposit onchain verification

* docs: block structure, header format

* docs: 403 policies, state reads

* docs: private rpc

* docs: contracts, network upgrades

* docs: batch frequency

* fmt: move withdrawals

* chore: remove unused sections from table of contents

* docs: update portal language

* docs: update sequencer controls language

* docs: remove privacy dir, add trust assumptions

* docs: update trust assumptions

* docs: deposit, withdrawal sequence diagram

* docs: separate withdrawals/deposits and encrypted variants

* docs: update sequence diagrams

* Update docs/specs/zone_spec.md

Co-authored-by: dankrad <[email protected]>

* Update docs/specs/zone_spec.md

Co-authored-by: dankrad <[email protected]>

* docs: update withdrawal diagram

* docs: fix revealTo, formatting

* docs: disabled, restricted methods

* docs: zone upgrade details

* docs: diagram labels

---------

Co-authored-by: dankrad <[email protected]>

Author: 0xKitsune