[UI] uiSchema params for overview property are overwritten by ui code

[JC-wk]

Describe the bug
in ui/app/src/components/shared/create-update-resource/ResourceForm.tsx the uiSchema is overwritten for the overview field, meaning other custom uiSchema cannot be set for it.

  const uiSchema = (template && template.uiSchema) || {};
  uiSchema.overview = {
 "ui:widget": "textarea",
}
``

**Steps to reproduce**
Setting the below has no effect because the ui overwrites it with `"ui:widget": "textarea"` 

"uiSchema": {
"overview": {
"ui:emptyValue": ""
}

see https://github.com/microsoft/AzureTRE/issues/4826#issuecomment-3840891730
**Azure TRE release version (e.g. v0.14.0 or main):**
main

**Deployed Azure TRE components - click the (i) in the UI:**
latest