[Log Parsing Pipelines] Pipeline preview should have more samples

[raj-k-singh]

Bug description

Right now pipeline previews use the latest 5 logs matching the pipeline filter as sample logs that get processed and shown.

It is not uncommon for a pipeline filter to match a significant number of logs that it doesn't end up processing (eg: the same service can end up emitting many kinds of logs, only some of which have pipeline processors targeting them)
In such cases, it is not guaranteed to have a processed log within the last 5 logs used as a sample.

Expected behavior

There should be some way for the user to get more samples - by pagination or infinite scroll for example.