Partial progress towards completing an assertions audit

[tedinski]

Description of changes:

I'm headed out on vacation, so this is a partial PR. It might be mergeable as-is though, it just doesn't complete the whole task.

1. Concentrates everything assertion/assumption/etc fully in assert.rs
2. There are a few PropertyClasses that I'm not sure if we want necessarily. Do we need/want to distinguish some of our instrumented assertions from just the default Assertion? I could go either way. I've added a fair number of TODOs to think about.

Resolved issues:

• Does not yet complete #1056
• Fixes #1208
• Fixes #1349

Call-outs:

Testing:

• How is this change tested? existing tests, some of which required changes due to new behavior

• Is this a refactor change? yes but also no since wrong-behaviors were identified

Checklist

• [ ] Each commit message has a non-empty body, explaining why the change was made
• [ ] Methods or procedures are documented
• [ ] Regression or unit tests are included, or existing tests cover the modified code
• [ ] My PR is restricted to a single feature or bugfix

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.