Long Vector Execution Tests: Derivative and Quad Operators

[alsepkow]

This issue captures adding long vector exec tests for the Derivative and Quad operator intrinsics

The most recent Long Vector test plan document should be referenced when implementing: Long Vector Test Plan

Notes:

• The derivative ops are unary ops. Input and output type match.
• QuadReadLaneAt is a binary op as it also takes an index. Input type matches output type.
• All the other QuadReadLane ops are unary. Input type matches output type.
• Open question: Documentation makes it look like these are all float only ops. Confirm that.

[pow2clk]

Getting the derivatives right with implementation dependent behavior is tricky. I encourage stealing from the existing execution tests.

Need to test compute, pixel shaders, and even mesh/amp where supported. Need testing when helper lanes are involved and when they are not.