[BUG] ApiCaller accept invalid http method which cause dashboard crash

[Hailong-am]

What is the bug?
ApiCaller don't do validation on http method. when we pass an invalid http method in request body that cause dashboard server crash

How can one reproduce the bug?

1. start dashboard server
2. run below command

curl 'http://localhost:5601/api/ism/apiCaller' \
  -H 'Accept: */*' \
  -H 'Accept-Language: en-US,en;q=0.9' \
  -H 'Authorization: Basic YWRtaW46YWRtaW4=' \
  -H 'Content-Type: application/json' \
  -H 'osd-version: 3.0.0' \
  -H 'osd-xsrf: osd-fetch' \
  --data-raw '{"data":{"method":"a invalid http method here","path":"/_plugins/_im/lron/LRON%3Aindices%3Adata%2Fwrite%2Freindex","body":{"lron_config":{"action_name":"indices:data/write/reindex","channels":[{"id":"cAkHvYgB0GBNl905IY7P"}],"lron_condition":{"failure":true,"success":true}}}},"endpoint":"transport.request"}'

3. dashboard crash

TypeError: Method must be a valid HTTP token ["a invalid http method here"]
    at new NodeError (node:internal/errors:387:5)
    at new ClientRequest (node:_http_client:215:13)
    at Object.request (node:https:357:10)
    at HttpConnector.request (/Users/ihailong/code/OpenSearch-Dashboards/node_modules/elasticsearch/src/lib/connectors/http.js:182:23)
    at sendReqWithConnection (/Users/ihailong/code/OpenSearch-Dashboards/node_modules/elasticsearch/src/lib/transport.js:263:35)
    at Object.utils.applyArgs (/Users/ihailong/code/OpenSearch-Dashboards/node_modules/elasticsearch/src/lib/utils.js:188:19)
    at wrapper (/Users/ihailong/code/OpenSearch-Dashboards/node_modules/lodash/lodash.js:5255:19)
    at processTicksAndRejections (node:internal/process/task_queues:78:11)
 server crashed  with status code 1

What is the expected behavior?
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What is your host/environment?

• OS: [e.g. iOS]
• Version [e.g. 22]
• Plugins

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