Statement instance order and lex order map

[jdsteve2]

NOTE: This PR has been subsumed by #479, which targets main. This PR still targets new-dependency-and-nest-constraint-semantics-development.

What's changed:

Last merged PR (parent of this PR):

• Generate a pairwise schedule for each provided pair of statements. Ignore concurrency.

This PR:

• Generate three pairwise schedules for each provided pair of statements which handle intra-thread, intra-group, and global ordering.
• Generate three lex order maps (LOM), one for each pairwise schedule
  • A LOM represents a lexicographic ordering as a map from each point in the ordering to every point occurring later in the ordering.
  • The LOM for the intra-thread case is a standard big-endian lexicographic ordering. The LOMs for the intra-group and global cases begin as a standard ordering, and then certain pairs are removed.
• Using each pairwise schedule and its corresponding LOM, create a statement instance ordering, which maps each statement instance to all statement instances that occur later.

Note: The use of SIOs for dependency checking is not part of this PR.

Moved to github from old gitlab MR.

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Subsumed by #479.