Deprecate ExprSchemable::metadata

[alamb]

Is your feature request related to a problem or challenge?

• Similar to Deprecate ExprSchemable:: data_type_and_nullable #18844

ExprSchemable::metadata simply calls through to to_field and thus makes the API more complicated for no real gain

datafusion/datafusion/expr/src/expr_schema.rs

Lines 421 to 424 in 4f95e6d

	fn metadata(&self, schema: &dyn ExprSchema) -> Result<FieldMetadata> {
	self.to_field(schema)
	.map(|(_, field)| FieldMetadata::from(field.metadata()))
	}

Describe the solution you'd like

We should deprecate metadata to encourage people to use to_field directly

The deprecation guidelines are here: https://datafusion.apache.org/contributor-guide/api-health.html#deprecation-guidelines

Describe alternatives you've considered

1. Add deprecation notice to ExprSchemable::metadata
2. Add a note / example in the docs for ExprSchemable::to_field that notes how to get Metadata
3. Update all existing code locations that call ExprSchemable::metadata to use ExprSchemable::to_field instead

Additional context

No response

[BipulLamsal]

sure i can take this ticket