Remove clear on mock page/array

since we use a shared cluster, calling clear on the mock array / page recycler can cause removing a valid on going reference, and then when its released, the release will fail because it can't be found.
There is no real reason to call clear, checking if pages/arrays have been released takes the snapshot behavior here into account.
This change also makes sure we don't use the mock classes in places where we don't really release.

Note, with this change DoubleTermsTests fails, since it causes failures when creating aggs in the pre process phase, causing obtained arrays not to be released. This needs to be fixed before pulling this change in.