fix(templating)!: return json, not go structs #21901

Job	Run time
argo-images (argoexec)	2m 43s
argo-images (argocli)	2m 58s
Get changed files	5s
Lint	2m 43s
Codegen	3m 25s
Windows Unit Tests	11m 22s
Unit Tests	3m 14s
UI	0s
E2E Tests (test-executor, minimal)	12m 20s
E2E Tests (test-corefunctional, minimal)	11m 19s
E2E Tests (test-functional, minimal)	19m 21s
E2E Tests (test-api, mysql)	5m 40s
E2E Tests (test-cli, mysql)	10m 25s
E2E Tests (test-cron, minimal)	5m 19s
E2E Tests (test-examples, minimal)	5m 52s
E2E Tests (test-plugins, plugins)	3m 49s
E2E Tests (test-java-sdk, minimal)	3m 22s
E2E Tests (test-python-sdk, minimal)	2m 56s
E2E Tests (test-executor, v1.26.15+k3s1, minimal)	13m 27s
E2E Tests (test-corefunctional, v1.26.15+k3s1, minimal)	12m 20s
E2E Tests (test-functional, v1.26.15+k3s1, minimal)	20m 23s
E2E Tests - Composite result	1s
	2h 33m 4s

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