refactor: Add inline comments, remove info.xml

[DaveSkender]

Description

The PR is primarily for code cleanup and to ensure wide consistent adoption of new conventions for inline XML commenting to replace the difficult to maintain info.xml files and to make better use of the new C#10 record class where appropriate to maximize their utility / compatibility with streaming applications.

Done when:

• wait, to rebase from v3 after merge of feat: Full chain streaming prototypes #1092
• add a top-level Interface or virtual where needed to ensure mockable.
• all info.xml files are replaced with inline XML comments using the /// convention, making good use of cref and <inheritdoc/> from the IStockIndicators interface descriptions.
• all public classes have /// comments (e.g. utility, streaming classes)
• ensure all public data classes are converted to record type where possible
• restore use of [Serializable] attribute, if needed