Remove cleaning `\\` or `\` in `got` and `want` strings of test cases.
This is to prevent future the need to manually clean strings before
comparing. This also allows us to be aware of the amount of backspace to
prevent accidental escaping in src code.
Update integration test that is affected. This includes moving the
`want` of test cases for `my-param-tool` invocation to each sources
since spanner have a different format (return id as strings instead of
int).
Update http tools `Invoke` method.
* use `json.Unmarshal` for response body that are either list or json
map. This will allow us to return lists as is (e.g. `[{map}]` instead of
having to nest it in an additional list (e.g. `[]any{ [{map}] }`)
* for response body that are strings or fail to unmarshal, return it as
is.
