This moves the location of the bytecode-offset translation that turns
offsets of back jumps into offsets of loop headers. This translation is
now done by the {BytecodeGraphBuilder} after loop analysis has been
performed. It safes one redudant iteration over the bytecode array. Note
that this changes the semantics of the BailoutId used as an {osr_ast_id}
throughout the compiler pipeline for OSR from Ignition.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2465913002
Cr-Commit-Position: refs/heads/master@{#41431}