Support X + Y, X >> Y and X >>> Y operations for Int8 type

Other operations such as X - Y will be also supported by this
change. But they are not tested yet.

I wanted to support one operation per a commit but this change is the
minimum change. :<
Add a test for X - Y for Int8 type
Add a test for X * Y for Int8 type
Add a test for binary operation for Int8 type

Operation: X / Y
Add a test for binary operation for Int8 type

Operation: X % Y
Add a test for binary operation for Int8 type

Operation: X << Y
Add a test for binary operation for Int8 type

Operation: X | Y
Add a test for binary operation for Int8 type

Operation: X ^ Y
Add a test for binary operation for Int8 type

Operation: X & Y

TODO: Add tests for assign family such as +=.
Add a test for binary assign operation for Int8 type

Operation: X += Y
Add a test for binary assign operation for Int8 type

Operation: X -= Y
Add a test for binary assign operation for Int8 type

Operation: X *= Y
Add a test for binary assign operation for Int8 type

Operation: X /= Y
Add a test for binary assign operation for Int8 type

Operation: X %= Y
Add a test for binary assign operation for Int8 type

Operation: X <<= Y
Add a test for binary assign operation for Int8 type

Operation: X >>= Y
Add a test for binary assign operation for Int8 type

Operation: X >>>= Y
Add a test for binary assign operation for Int8 type

Operation: X &= Y
Add a test for binary assign operation for Int8 type

Operation: X |= Y
Add a test for binary assign operation for Int8 type

Operation: X ^= Y