Up until now all type conversions (i.e. ToNumber, ToString and friends)
had their own specific call interface descriptors, where some of them
had to match (i.e. ToString and NumberToString have to use the same
argument register). Instead of all the different descriptors, it's
sufficient to have a single TypeConversionDescriptor instead.

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/1823523002

Cr-Commit-Position: refs/heads/master@{#34916}