[REVIEW] Introducing host API for PCG (#1767)

This PR introduces following changes
1. Adds support for calling PCG RNG API from the host
2. Adds a test for verifying host API
3. Fixes a bug in Normal PDF deviate function for integers (`custom_next`)
4. Adds a wide 64-bit multiplication function for both host and device
5. Adds a test for 64-bit wide multiplication on host and device

Authors:
  - Vinay Deshpande (https://github.com/vinaydes)
  - Artem M. Chirkin (https://github.com/achirkin)

Approvers:
  - Matt Joux (https://github.com/MatthiasKohl)
  - Artem M. Chirkin (https://github.com/achirkin)
  - Corey J. Nolet (https://github.com/cjnolet)

URL: #1767