Expand DSched interface for managing auxiliary functions

Expand DSched interface for managing auxiliary functions

Summary:
Changed DSched interface for managing auxiliary functions to allow separate auxiliary functions for single actions (applicable to the next shared access by a specific thread) and repeating actions (applicable to all subsequent shared accesses).

[Note: I have a dependent diff that depends on both this diff and the diff for dynamic MPMCQueue (/D3462592). I don't think I can submit a diff that depends on multiple diffs that haven't landed yet. So, I'll wait until this one lands.]

Reviewed By: djwatson

Differential Revision: D3792669

fbshipit-source-id: 52654fffda2dc905b19ff91f4459f15da11f7735