Translates code of the form 'if (x === undefined)' into the JumpIfUndefined
bytecode, and similarly for comparisons with null. Also adds bytecodes for
JumpIfNotUndefined / Null.

Moves the peephole optimization for CompareUndefined out of the peephole
optimizer and into the BytecodeGenerator, having the side-effect of enabling
it for comparisons with undefined on both side of the compare operation.

BUG=v8:6107

Review-Url: https://codereview.chromium.org/2793923002
Cr-Commit-Position: refs/heads/master@{#44341}