Enabling arena allocator

[Igor Gutorov]

The allocator can be switched here:

ort/src/session/mod.rs

Lines 252 to 256 in 90b8d30

 /// Set the session's allocator. Defaults to [`AllocatorType::Device`]. 
 pub fn with_allocator(mut self, allocator: AllocatorType) -> Result<Self> { 
 	self.allocator = allocator; 
 	Ok(self) 
 } 

but if I'm not mistaken, self.allocator is not used anywhere, and actually building the Session just creates Allocator::default():

ort/src/session/mod.rs

Line 487 in 90b8d30

 let allocator = Allocator::default(); 

Am I mistaken, or does with_allocator not do anything?

[Igor Gutorov]

Thanks a lot for implementing it this quickly!