Separate Execution Gas Price and DA Gas Price into separate newtypes to add clarity

[MitchTurner]

It's been suggested that we separate the two just to help organize the code a bit better. Instead of just dealing withu64 everywhere, it could help the reader to have types to communicate everywhere in the code the purpose of the numbers.

[feifies]

您好，我想要修复 Issue #2382，但对项目的代码结构还不太熟悉，能否提供相关的文件名或模块的指引？非常感谢！