Mismatch type description for Cognito CognitoEventUserPoolsPreTokenGenV2 Event

There is a type mismatch for [`claims_to_add_or_override`](https://github.com/aws/aws-lambda-rust-runtime/blob/61855c2eabfc725f93cad6deabb7d6fa203e35a9/lambda-events/src/event/cognito/mod.rs#L572) in [CognitoEventUserPoolsPreTokenGenV2](https://github.com/aws/aws-lambda-rust-runtime/blob/61855c2eabfc725f93cad6deabb7d6fa203e35a9/lambda-events/src/event/cognito/mod.rs#L473) event. `claims_to_add_or_override` should accept any of the json types instead of only strings.

The [documentation at AWS](https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-pre-token-generation.html#cognito-user-pools-lambda-trigger-syntax-pre-token-generation) mentions the following type description for the event as:
```json
{
"request": {
"userAttributes": {
"string": "string"
},
"scopes": ["string", "string"],
"groupConfiguration": {
"groupsToOverride": ["string", "string"],
"iamRolesToOverride": ["string", "string"],
"preferredRole": "string"
},
"clientMetadata": {
"string": "string"
}
},
"response": {
"claimsAndScopeOverrideDetails": {
"idTokenGeneration": {
"claimsToAddOrOverride": {
"string": [accepted datatype]
},
"claimsToSuppress": ["string", "string"]
},
"accessTokenGeneration": {
"claimsToAddOrOverride": {
"string": [accepted datatype]
},
"claimsToSuppress": ["string", "string"],
"scopesToAdd": ["string", "string"],
"scopesToSuppress": ["string", "string"]
},
"groupOverrideDetails": {
"groupsToOverride": ["string", "string"],
"iamRolesToOverride": ["string", "string"],
"preferredRole": "string"
}
}
}
}
```

##### Accepted datatypes:
* String
* Number
* Boolean
* Array of strings, numbers, booleans, or a combination of any of these
* JSON

#### Proposed Solution
```diff
- pub claims_to_add_or_override: HashMap
+ pub claims_to_add_or_override: HashMap
```

Start in lambda-events/src/event/cognito/mod.rs at CognitoEventUserPoolsPreTokenGenV2 and its claims_to_add_or_override field, then compare the field with the AWS event schema linked in the issue. Done means the field accepts the documented JSON value types instead of only strings and the existing event behavior remains compatible.

Written by the indexing model from the issue text.