This PR modifies every test in `builtin/credentials/approle/path_role_test.go` with new validation checks to ensure that approle/path_role successful responses align with the declared response schema.
It also introduces a test helper in `sdk/helper/testhelpers`:
```go
func FindResponseSchema(t *testing.T, ...)
```
This test helper will be useful for all plugins that require similar response schema validation in tests.
### Background
This PR is part of the ongoing work to add structured responses in Vault OpenAPI (VLT-234)
This pull request adds 3 functions (and corresponding tests):
`testhelpers/response_validation.go`:
- `ValidateResponse`
- `ValidateResponseData`
field_data.go:
- `ValidateStrict` (has the "strict" validation logic)
The functions are primarily meant to be used in tests to ensure that the responses are consistent with the defined response schema. An example of how the functions can be used in tests can be found in #18636.
### Background
This PR is part of the ongoing work to add structured responses in Vault OpenAPI (VLT-234)
