SelectivePacker: Consistently check whether TES entries are explicitly requested

SelectivePacker only explicitly checked whether KeyedContainers and RecSummary it had access to were explicitly requested -- other TES entries were added to the packed output regardless of any request, as soon as they existed in the TES. This MR moves this check 'upstream' in the code so that this is done in the same place for every type of object.

As a result, it may be that objects other than KeyedContainer and RecSummary are no longer implicitly copied, and the configuration may need to be adapted to explicitly copy them instead. To help with this, a new property 'AlwaysPack' has been added which specifies locations that should be packed regardless of any Hlt/Spruce decisions.

Must be applied in conjunction with Moore!2281 (merged) -- which also depends on !4149 (merged)