Complete and Require Javadocs

[samfreund]

Description

Meta

Merge checklist:

• Pull Request title is short, imperative summary of proposed changes
• The description documents the what and why
• If this PR changes behavior or adds a feature, user documentation is updated
• If this PR touches photon-serde, all messages have been regenerated and hashes have not changed unexpectedly
• If this PR touches configuration, this is backwards compatible with settings back to v2024.3.1
• If this PR touches pipeline settings or anything related to data exchange, the frontend typing is updated
• If this PR addresses a bug, a regression test for it is added

[mcm001]

A lot of these docs are just re-stating the function name. Like of course the constructor makes a new X

Try to see how the javadocs can explain more than just surface level things.