[Access] Add support for pruning the Registers DB

[peterargue]

Problem Definition

Currently, the registers db stores data for all account updates starting from when indexing was initialized. This is great for an archive node, but produces a lot of data over time especially as the time between network upgrades increases. To keep disk and memory usage at more manageable levels, some operators may prefer to only keep a recent subset of the data.

Proposed Solution

Add support for pruning the registers DB to a configurable amount of history.

The operator should have control over the following new settings:

• pruneThreshold which sets the number of blocks of history to keep
• pruneInterval which sets the frequency of pruning rounds. This will be configured as a number of blocks of unpruned data below the threshold.
• pruneThrottleDelay which sets a delay the pruner should use while iterating the db to reduce load on the overall system.

These settings will use a reasonable defaults so the operator is not required to configure them unless the way custom behavior.

• [Access] Enforce pruneThreshold in registerDB queries #6066
• [Access] Add registerDB pruning module #6068
• [Access] Test and tune pruning on live network data. #6067