Fix *context* operators have broken links for jumps (global-jumps to relative-jumps)

[kirillzhosul]

Currently, parser and core has context operators (e.g if, while...) that contains jumps_to_operator_idx which is global and may be shifted after currently processing operator leading to global link is broken and result is that codegen or anything other cannot emit anything related to that instruction.

Solution would be to refactor global-jumps into relative-jumps related to the current function (this is also quite useful for codegen backends and local labels to jump)