Revert "Asynchronously write batches to NuDB. (#4503)"

[mtrippled]

This reverts commit 1d9db1b.

High Level Overview of Change

Revert code that introduces problems associated with online deletion.

Context of Change

The bug was introduced in PR #4503, which causes writes to block during online deletion. In turn, this delays persisting records to disk during consensus, which causes node desyncs.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

Run online deletion as normal. It should stay stable, and revert to behavior from 1.12 and previous.

Future Tasks

If we proceed with this revert, there will there be no reason to consider #4762.

Closes #4762

[intelliot]

QA will check to see how this can be tested

[ximinez]

Clean revert.

[intelliot]

Internal tracker: RPFC-80

[intelliot]

Perf SignedOff: "I think 4882 is good to go"