[Tensor Pool] Add expose/persist concept

[Tensor Pool] Add expose/persist concept

This patch add expose/persist concept to the tensor pool and manager.

When a tensor is exposed, this means that the tensor is gauranteed to
remain valid max_exec where max_exec is the value passed along allocateTensors(max_exec);

**Self evaluation:**
1. Build test: [X]Passed [ ]Failed [ ]Skipped
2. Run test: [X]Passed [ ]Failed [ ]Skipped

Signed-off-by: Jihoon Lee <jhoon.it.lee@samsung.com>