This increases the size of addressable constant pool entries for jumps
to match other bytecodes using operands indexing the constant pool.

This change also introduces reservations for constant pool entries.
Reservations are used for forward jumps to ensure a constant pool entry
will be available when the jump target (label) is bound and the jump is
patched up in the bytecode array.

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1546683002

Cr-Commit-Position: refs/heads/master@{#33125}