Check that no documentation is lost

[verytactical]

• Check every page of old docs has landed somewhere in new docs
• Check that all old pages redirect to relevant new pages — replace all TODO and issue link destinations with actual routes as they appear. Also, pay attention to the "/" destinations, since those often mean that the original page was deleted and no replacement was needed (or not found)
• (Right before release) Re-enable the redirects check against the upstream docs.json structure introduced in feat(ci): add redirect checks and reconstruct redirects array for all links from the previous TON Docs #1084

[reveloper]

Created old documentation list for matching with new pages: https://docs.google.com/spreadsheets/d/1M-gmnC3nLefCWJBTzHiwMLX4vH2aZYqqCdp4uzQX3Iw/edit?gid=843997444#gid=843997444

[reveloper]

Document updated till October 2 commits