Avoid unnecessary function calls in code generation

In many parts of the codebase for code generation, we are splitting the code to avoid exceptions due to the 64KB method size limit. This is generating a lot of methods which are called every time, even though sometime this is not needed. As pointed out here: https://github.com/apache/spark/pull/19752#discussion_r153081547, this is a not negligible overhead which can be avoided.

In this JIRA, I propose to use the same approach throughout all the other cases, when possible. I am going to submit a PR soon.