Add explicit state in BytecodeSourceInfo to simplify checks for
validity and whether a statement or expression position.

Remove BytecodeSourceInfo::Update which inherited rules for updating
source position information during bytecode building.

BUG=v8:4280
LOG=N

Review-Url: https://codereview.chromium.org/2048203002
Cr-Commit-Position: refs/heads/master@{#37136}