[Grid] Support Java records in GridEditor

[vursen]

Describe your motivation

Starting from 24.5, Binder officially supports Java records. However, GridEditor needs an update before developers can use them smoothly.

Since records are immutable by design, they seem to make sense primarily in buffered mode, which was originally designed to prevent changes to beans until save() is explicitly called. Using records in buffered mode today leads to exceptions when calling save() because it uses Binder API that's incompatible with records.

Describe the solution you'd like

• Update buffered mode to work with Java records
• Add a note in the setBuffered() JavaDoc recommending buffered mode for records

Furthermore, editItem(T item) could throw an exception requiring to enable buffered mode if item is a record. However, there is evidence that some applications are already using records in non-buffered mode with custom workarounds. The exception will break them forcing developers to rewrite potentially a significant part of the code.

Additional context

#6755 (comment)