[ML][Common] Add TensorsInfo.getTensorSize

[ML][Common] Add TensorsInfo.getTensorSize

ACR: TWDAPI-273

Test code:
var ti = new tizen.ml.TensorsInfo();
ti.addTensorInfo("tensor1", "UINT8", [1, 1])
console.log(ti.getTensorSize(0))
ti.addTensorInfo("tensor2", "UINT8", [2, 3, 4])
console.log(ti.getTensorSize(1))
ti.addTensorInfo("tensor2", "FLOAT32", [2, 3, 4])
console.log(ti.getTensorSize(2))
console.log(ti.getTensorSize(-1))

[Verification] Built successful. Tested in Chrome Dev console.

Change-Id: I841da30d03a0590cea66ec6217130163a87f59ec
Signed-off-by: Rafal Walczyna <r.walczyna@samsung.com>