[DOC] Update error_trace URL parameter description

[xuezhou25]

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Coming from this issue#4255
The description of Stack traces in OpenSearch documentation is not comprehensive and may leading to some misunderstanding.

"To include the error stack trace in the response when an exception is raised, add error_trace=true to the request URL." is right.
It is better to add the description of Config setting: If there is a setting of http.detailed_errors.enabled: false in config file, the error_trace url request will be rejected.

The detailed logic will be:
When the config setting http.detailed_errors.enabled: false, the request of error_trace=true will not contain the detailed error message.

$ curl "http://localhost:9200/opensearch/_search?error_trace=false"
{"error":"IndexNotFoundException[no such index [opensearch]]","status":404}

$ curl "http://localhost:9200/opensearch/_search?error_trace=true" 
{"error":"error traces in responses are disabled.","status":400}   

This code regarding to this setting is from: https://github.com/opensearch-project/OpenSearch/blob/2.2.1/server/src/main/java/org/opensearch/rest/RestController.java#L368-L375

When there is no config setting for http.detailed_errors.enabled or http.detailed_errors.enabled: true, the response of URL parameter will contain detailed error message:

$ curl "http://localhost:9200/opensearch/_search?error_trace=true&pretty"
{
  "error" : {
    "root_cause" : [
      {
        "type" : "index_not_found_exception",
        "reason" : "no such index [opensearch]",
        "index" : "opensearch",
        "resource.id" : "opensearch",
        "resource.type" : "index_or_alias",
        "index_uuid" : "_na_",
        "stack_trace" : "[opensearch] IndexNotFoundException[no such index [opensearch]]\n\tat org.opensearch.cluster.metadata.IndexNameExpressionResolver$WildcardExpressionResolver.indexNotFoundException(IndexNameExpressionResolver.java:1067)\n\tat org.opensearch.cluster.metadata.IndexNameExpressionResolver$WildcardExpressionResolver.innerResolve(IndexNameExpressionResolver.java:1004)

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

[rursprung]

please note that there's more to this: if the config option is set then not just the error_trace HTTP parameter is disabled but also some error messages are no longer being returned. see opensearch-project/OpenSearch#4545 for further details (this might be a bug, but i guess for now you can document the status quo and it can be updated once the bug ticket has been addressed one way or the other?)