refactor(codegen): inline contract router

[anton-trunov]

This requires inlining receivers as well.
Reduces gas usage of the Jetton benchmarks.
But increases gas usage for Escrow (I think we can live with it for now, until #1866 is resolved).

Issue

Closes #1587.

Gas Benchmarks

Checklist

• I have run all the tests locally and no test failure was reported
• I have run the linter, formatter and spellchecker
• I did not do unrelated and/or undiscussed refactorings (but I really wanted to do it)

[Kaladin13]

General logic is solid, good thing we have #1949 since we will catch all possible router bugs there, if there are any, after this massive codegen changes

Few notes in review

[Kaladin13]

Good to go!