Runtime fails to serialize json into hashtable for Durable activities

#### Repro steps

Provide the steps required to reproduce the problem:

1. Create a powershell function with the following parameters
2. add an http trigger function with following code:
```powershell
using namespace System.Net
param($Request, $TriggerMetadata)
Push-OutputBinding -Name Response -Value ([HttpResponseContext]@{
StatusCode = [HttpStatusCode]::OK
Body = $Request.Body.GetType()
})
```
3. call the function with something like this:
```
{"buildId":"id","sourceVersion":"version","scopes":["/subscriptions/fdbb6770-4977-44e9-9ee4-4cf0fcc1e6b3","/subscriptions/51c2c6a2-e6bd-492d-8a9d-0b02d6a325d8"],"certValue":"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"}
```

#### Expected behavior

returns `System.Collections.Hashtable`

#### Actual behavior

returns `System.String`

#### Known workarounds

forcefully cast to an object with `$Request.Body | ConvertFrom-Json`

#### Related information

https://docs.microsoft.com/en-us/azure/azure-functions/functions-reference-powershell?tabs=portal#request-object

* using powershell
* **works** with a simpler json payload (ie: `{"name": "please_work"}`)
* json is valid (RFC 8259)
* bindings:
```
{
"bindings": [
{
"authLevel": "function",
"type": "httpTrigger",
"direction": "in",
"name": "Request",
"methods": [
"get",
"post"
]
},
{
"type": "http",
"direction": "out",
"name": "Response"
}
]
}
```