Change vector constructors to take queue argument

This changes the vector<T> constructors which copy or initialize
data to take a queue argument used for performing the operations.

Previously they just took a context argument used to initialize the
buffer and then created a new command queue to use. This improves
performance by not requiring a new command queue and also fixes issues
when performing operations on a different command queue while the
vector was still being initialized.
Fix sign comparison warnings in tests
Add test for generate() with pair<T1, T2>