We need functionality to relocate existing nmethods within CodeCache.
The main use case is to group hot nmethods in a separate code heap. Without this functionality, we need to use recompilation which is expensive for big methods.

Other uses cases:
- Save C1 nmethods when they are replaced by C2 nmethods having speculative code.
- Save C2 nmethods being removed as cold.

We might not need to support relocation of OSR nmethods.