FEAT: Unified small/large undo logs

[pbalcer]

Unified small/large undo logs

Rationale

Currently we have two separate different snapshot undo logs: one for small ranges and one for huge.
The small one combines multiple snapshots into a single allocations by employing a cache of a predefined size. For snapshots exceeding a threshold, we simply allocate an entirely new object for that single range. This leads to a) code duplication, b) space inefficiencies and c) unnecessary logic.

Description

The reason for this separation is mostly due to backward compatibility, but since we are rewriting the lanes anyway, we can once again take a stab at simplifying this code.

We can entirely remove the huge snapshots undo log by removing the small range threshold and extending the logic to:

• allocate larger undo logs when snapshotting a large range
• splitting ranges so that the snapshots can be packed in a space efficiently manner

API Changes

The tx.cache.threshold entry point is going to become deprecated after this change. Setting it should have no effect.

Implementation details

To efficiently use the allocation classes mechanism, the size of a cache calculated as follows:
MAX(tx.cache.size, align_up(snapshot_size, tx.cache_size)).