Added Label, Continue, Break support

[b-temirov]

This PR is not dependent on #2 and the branch was creating from an existing hkmc2 branch.

[Derppening]

Please don't include HkScratch.mls in the PR. Either attach the code snippet as part of the PR description, or add a file under hkmc2/shared/src/test/mlscript/wasm with your test cases.

[Derppening]

Why do we need special logic when a continue is present? Looking at the equivalent implementation in JSBuilder it appears that we can just treat a label as a label + loop + break?

[Derppening]

I don't think you should manually create label names like this. You can probably follow how JSBuilder does it:

• scope.allocateName on the label
• Generate a block + loop
• When you encounter a break you br to the allocated name of the label
• When you encounter a continue you br 0 to the loop to continue executing the loop

Unlike with other index spaces, indexing of labels is relative by nesting depth, that is, label 0 refers to the innermost structured control instruction enclosing the referring branch instruction, while increasing indices refer to those farther out. [...] The exact effect depends on that control construct. In case of 𝖻𝗅𝗈𝖼𝗄 or 𝗂𝖿 it is a forward jump, resuming execution after the end of the block. In case of 𝗅𝗈𝗈𝗉 it is a backward jump to the beginning of the loop.

https://webassembly.github.io/spec/core/syntax/instructions.html#syntax-instr-control

• Once you finish processing the body block, break out to continue executing rest

[LPTK]

Thanks @Derppening; I'll review when they address your comments.