php 8.2: explicitly declaring variables

[torvista]

I've done the necessary for products so far, making all variables protected until an error demands public.

[lat9]

I'm pretty sure (i.e. not 100%) that all the DbIo admin tools make use solely of the DbIo handlers' public methods to 'do their thing'. As you indicated, protected is preferred unless there's some compatibility issue that would require making a variable public.

[torvista]

I've only used products and OptionsStock handlers. For those I put the definitions as demanded by the debug logs. A few need to be public. I've done a branch in my fork with these changes, and one fix for an unrelated debug