Use compact_str instead of String as Schema's field

[fjchen7]

It seems that in most cases, the Schema's field are not very long. The atc-router sets it as String, which allocates memory on the heap during each initialization and cloning.

In this scenario, I suggest using compact_str instead of String. CompactString from compact_str is a mutable string, but it has a great feature: when the string is less than 24 bytes (which I believe should cover most cases), it will be stored on the stack. This is more efficient than performing operations on the heap during initialization or cloning.

Similarly, some field of Match and Context can also be modified.

Considering that there are numerous String clones in the code, I think using compact_str instead could bring a noticeable improvement in efficiency.