[Change Proposal] Allow 'terminate' ingest processor

[andrewkroh]

Support the terminate processor (added in 8.16.0) in Fleet integration ingest pipelines. This is necessary to implement elastic/integrations#12083 (comment) which replaces the fail processor with terminate for clearer error messages.

The area of the package-spec that needs enhanced is:

package-spec/spec/integration/elasticsearch/pipeline.spec.yml

Lines 9 to 62 in 7eb29ca

	processor:
	type: object
	additionalProperties: false
	maxProperties: 1
	properties:
	append: { type: object }
	attachment: { type: object }
	bytes: { type: object }
	circle: { type: object }
	community_id: { type: object }
	convert: { type: object }
	csv: { type: object }
	date: { type: object }
	date_index_name: { type: object }
	dissect: { type: object }
	dot_expander: { type: object }
	drop: { type: object }
	# enrich: false # Additional support needed.
	fail: { type: object }
	fingerprint: { type: object }
	# geo_grid: false # Support for geo shape fields needed.
	geoip: { type: object }
	grok: { type: object }
	gsub: { type: object }
	html_strip: { type: object }
	inference: { type: object }
	join: { type: object }
	json: { type: object }
	kv: { type: object }
	lowercase: { type: object }
	network_direction: { type: object }
	pipeline: { type: object }
	redact: { type: object }
	registered_domain: { type: object }
	remove: { type: object }
	rename: { type: object }
	# reroute: false # reroute_rules.yml should be used instead.
	script: { type: object }
	set: { type: object }
	# set_security_user: false # Applicable to packages?
	sort: { type: object }
	split: { type: object }
	trim: { type: object }
	uppercase: { type: object }
	urldecode: { type: object }
	uri_parts: { type: object }
	user_agent: { type: object }
	foreach:
	type: object
	properties:
	processor:
	$ref: "#/definitions/processor"

[andrewkroh]

Per https://github.com/elastic/package-spec/blob/main/CONTRIBUTING.md#change-proposals,

Discussion ensues and eventually we hope to reach some consensus.

I don't think there is anything controversial about this change, but wanted to follow the process ☑.

[efd6]

Already sent #847 before I saw this.