Convert remaining widget and formatter type migrations to MigrateField plugins

Problem/Motivation

The field migration plugin system hard-codes some plugin ID mapping in field migrations while an equivalent (and more maintainable) plugin system exists for the same reason.

This blocks #3202462: [PP-1] Provide option for contrib modules to map their D6 / D7 field formatter and widget plugin IDs to the equivalent D9 plugin ID and I also think it is only a leftover of times before the field migration plugin system.

Proposed resolution

Move the formatter and widget type mappings from the core formatter and widget migration plugin definitions into the corresponding @MigrateField plugin.

• d6_field_instance_widget_settings
• d7_field_instance_widget_settings
• d6_field_formatter_settings

(The d6_field_formatter_settings migration does not contain hard-coded mapping.)

Retain the static maps in the d6 migrations to maintain BC.

Remaining tasks

Patch
Review
Commit

User interface changes

Nothing.

API changes

Nothing.

Data model changes

Nothing.

Release notes snippet