upgrade misc utilities

[DaveSkender]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation, context, and sources of information or recipes.

Unblocks #983 and implements:

• make .SyncIndex() a public utility #984
• full series converter for results.Null2NaN() #981
• add or update unit tests (see Issue for more tasks)
• update documentation
• confirm whether the new use of ISeries is a good idea; it may be more confusing than useful (e.g. in custom quotes)

Breaking changes ⚠️

• IQuote.Date should be replaced by ISeries.Date if you have a customized (renamed) quote date property
• .ToTupleCollection(NullTo.Null2NaN) was replaced by a simpler .ToTupleNaN()

Checklist

• My code follows the existing style, code structure, and naming taxonomy
• I have put comments in my code, particularly for hard-to-understand areas
• I have performed a self-review of my code and included any verifying manual calculations
• I have added or updated unit tests that prove my fix is effective or that my feature works and achieves sufficient code coverage. New and existing unit tests pass locally and in the build (below) with my changes
• My changes generate no new warnings or other code analysis issues
• I have added or run the performance tests that depict optimal execution times
• I have made corresponding changes to the documentation

[DaveSkender]

This was implemented in v2.4.8