Closes gh-22657

This upgrades to Spring Data 2020.0.0 snapshots which required some
changes in Spring Data REST and Spring Data Elasticsearch before
upgrading to Spring Data Neo4j 6.

Closes gh-22299

See gh-22299

See gh-22299

Closes gh-22648

See gh-22647

Closes gh-22651

Closes gh-22645

Closes gh-22650

The overhead of build scans seems to have brought us right to the limit
of the Maven JVM's heap. As a result, builds are occasionally failing
as the heap's been exhausted.

This commit increases the JVM's max heap.

Closes gh-22649

See gh-22640

See gh-22640

Closes gh-22642

Closes gh-22641

Fixes gh-20229

This commit also switches to RSocket SNAPSHOTs and updates the
repository configuration to rely on "libs-snapshot", since the RSocket
SNAPSHOTs are mirrored there.

See gh-22640

Closes gh-22636

Closes gh-22633

Closes gh-22053

Fixes gh-22605

Closes gh-22630

Closes gh-22629

Closes gh-19557

* pr/22302:
  Polish "Update Neo4j health check to use the Neo4j Driver"
  Update Neo4j health check to use the Neo4j Driver

Closes gh-22302

See gh-22302

This commit replaces the Neo4j-OGM based health checks with one based on
the Neo4j Java driver. A Reactive variant is also added in this commit.

See gh-22302

Closes gh-22627

Closes gh-22626

This commit harmonizes dependency declarations for Jackson in the
actuator. Both Jackson and JSR 310 are back to optional in the core
actuator module and mandatory when using the auto-configuration.

Closes gh-22624

Closes gh-22623

Closes gh-22622

Closes gh-22591