fix: Address edge case in Shape.isInHttpBody() function

[dayaffe]

Describe the bug

The following comment was left in the code:
// TODO fix the edge case: a shape which is an operational input (i.e. has members bound to HTTP semantics) could be re-used elsewhere not as an operation input which means everything is in the body

Related issue: #710

Expected Behavior

fun Shape.isInHttpBody() checks to see if a shape is in the body of the http request. This should work for any valid shape with bound members.

Current Behavior

The TODO comment suggests that the code logic does not work properly when an input to operation is re-used elsewhere not as an input to an operation.

Reproduction Steps

This issue includes the work to re-produce this edge case which can likely be accomplished by creating a smithy file and corresponding test.

Possible Solution

No response

Additional Information/Context

No response

AWS SWIFT SDK version used

to be confirmed

Compiler and Version used

to be confirmed

Operating System and version

to be confirmed

[sichanyoo]

Moved to 2143