[BUG][Connector-V2][http] fix httpheader cover

[jackyyyyyssss]

#5368
HttpClientProvider if set param config will addbody will overwrite httpheader application/json Causing parameter loss
So the modification to 'param' and 'body' can only take effect one at a time

Check list

• Code changed are covered with tests, or it does not need tests for reason:
• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update change log that in connector document. For more details you can refer to connector-v2
  2. Update plugin-mapping.properties and add new connector information in it
  3. Update the pom file of seatunnel-dist
• Update the release-note.

[davidzollo]

LGTM
+1

[Hisoka-X]

Hi, could you add some test case in a follow up PR? To make sure the http request created by SeaTunnel always set right header and avoid regression. Also we can know what's behavior now easiler.

[jackyyyyyssss]

Hi, could you add some test case in a follow up PR? To make sure the http request created by SeaTunnel always set right header and avoid regression. Also we can know what's behavior now easiler.

ok i will imporve e2e test for cover this case