Rewrite the codebase with Tolk language

[lumtis]

Tolk language is now the official language used for TON smart contract programming: https://docs.ton.org/languages/tolk/overview

The language used for the current implementation, FunC, is no longer supported https://docs.ton.org/languages/func/overview

For further development of the TON gateway, rewriting the contract in Tolk should be considered.

Some docs on Tolk vs FunC: https://docs.ton.org/languages/tolk/from-func/tolk-vs-func