☂️ Consider making certain JNI routines leaf functions

[HosseinYousefi]

For some of the routines, we can generate both the normal and the leaf versions, and call each one depending on the situation. For example Set<PrimitiveType>ArrayRegion could be fast depending on the length of the region, maybe it makes sense to conditionally call one or the other based on this.

Candidates:

• FindClass
• DeleteGlobalRef
• Get<Member>ID
• GetStringLength
• GetArrayLength
• IsInstanceOf
• Primitive array operations
• Direct byte buffer operations
• String methods – especially when [vm/ffi] Investigate copy-free Strings sdk#39787 is landed

For jnigen, users should be able to specify if a method is leaf or not, this can be done as a part of jnigen transformation. However simply:

• Getting a field
• Setting a field
  Can be safely turned into leaf calls.

cc/ @dcharkes