BIP-1: Deprecate and remove FieldType metadata

[damccorm]

Deprecate and remove getMetadata on the FieldType.

• Add deprecation notice on the getMetadata field in version 2.21.0
• Remove the getMetadata field in 2.23.0

All usage of metadata should be replaced by 2.23.0 and use the portable beam schema options.

Imported from Jira BEAM-9704. Original Jira may contain additional context.
Reported by: alexvanboxel.
Subtask of issue #20022