[PROPOSAL] Turn warnings into errors

[dblock]

What/Why

What are you proposing?

Building the repo with ./gradlew build yields some warnings. Fix them and turn them into errors.

What problems are you trying to solve?

Avoid mistakes in the API specs during development time.

──  WARNING  ────────────────────────────────────────────── DefaultValueInUpdate
Shape: OpenSearch#Update
File:  /Users/dblock/source/opensearch-project/opensearch-api-specification/dblock-opensearch-api-specification/build/libs/opensearch-api-specification.jar!/META-INF/smithy/_global/update/operations.smithy:19:1

14| @xOperationGroup("update")
15| @xVersionAdded("1.0")
16| @suppress(["HttpUriConflict"])
17| @http(method: "POST", uri: "/{index}/_update/{id}")
18| @documentation("Updates a document with a script or partial document.")
19| operation Update {
  | ^

This update style operation has top-level input members marked with the @default
trait. It will be impossible to tell if the member was omitted or explicitly
provided. Affected members: [lang, refresh, require_alias, retry_on_conflict,
wait_for_active_shards]


──  WARNING  ────────────────────────────────────────────── DefaultValueInUpdate
Shape: OpenSearch#UpdateByQuery
File:  /Users/dblock/source/opensearch-project/opensearch-api-specification/dblock-opensearch-api-specification/build/libs/opensearch-api-specification.jar!/META-INF/smithy/_global/update_by_query/operations.smithy:20:1

15| @xVersionAdded("1.0")
16| @suppress(["HttpUriConflict"])
17| @http(method: "POST", uri: "/{index}/_update_by_query")
18| @documentation("Performs an update on every document in the index without chan…
19| for example to pick up a mapping change.")
20| operation UpdateByQuery {
  | ^

This update style operation has top-level input members marked with the @default
trait. It will be impossible to tell if the member was omitted or explicitly
provided. Affected members: [analyze_wildcard, conflicts, default_operator,
expand_wildcards, from, preference, requests_per_second, scroll_size, slices,
timeout, wait_for_active_shards, wait_for_completion]

SUCCESS: Validated 5401 shapes (WARNING: 2, NOTE: 1)

What is the developer experience going to be?

When building warnings cause build errors.

[nhtruong]

We're no longer using Smithy or Gradle