feat(stdlib): optimize sha256() and add keccak256()

[novusnota]

Issue

Closes #2767.

Checklist

• I have updated CHANGELOG.md
• I have documented my contribution in docs/ and made the build locally
• I have added tests to demonstrate the contribution is correctly implemented: this usually includes both positive and negative tests, showing the happy path(s) and featuring intentionally broken cases

[anton-trunov]

let's not change the FunC benchmarks in this PR

[novusnota]

let's not change the FunC benchmarks in this PR

The FunC benchmarks do not use the sha256() in any way, but they're compiled with stdlib.fc and stdlib_ex.fc that Tact use and that somehow affects them. I've opened a separate issue for that #2776.

If I revert the changes to benchmarked JSONs then CI won't pass :)

UPD: Looking for the source of trouble. As @anton-trunov pointed out, the reason might be that FunC's dead code elimination is quirky.

[anton-trunov]

UPD: Looking for the source of trouble. As @anton-trunov pointed out, the reason might be that FunC's dead code elimination is quirky.

Sorry, my bad. We just had a debugging session with @i582 and turns out the issues is the code dict internal structure is changed because of the changing method_ids

[Shvandre]

🐗