Rolldown used oxc Atom as the default string type.

After oxc-project/oxc#2295 and oxc-project/backlog#46, oxc Atom can't be used as a general purposed string type anymore. Not to mentioned that it lacks characteristics that bundler required.

To make updating oxc easier, we need to replace the current oxc Atom and use a new string type as the default. And to gain potential performance, the new string type should be

• friendly in parallel
• O(1) clone
• fast comparing
• fast hashing/pre-computed hash

Contexts:

• Due to scope hoisting, rolldown needs to pull out values from the every oxc ast identifier and store them in a different places. Since oxc Atom is not a general purposed string type anymore, we need to converting the Atom to a new string type. This costs some tax just for converting.