Added ClientErrorResponseException for 4xx response codes

[rhertogh]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌
Fixed issues	-

This PR allows to filter out client error response codes (4xx). E.g.

try {
    $client->api('https://test');
} catch (ClientErrorResponseException $e) {
    // Handle client error response
}

[what-the-diff]

PR Summary

• Enhanced Error Handling in BaseOAuth
  The sendRequest() method in src/BaseOAuth.php has been revised to include more specific handling of different error types. This will provide clearer, more targeted error messages based on the type of error that occurred, which should result in easier troubleshooting and issue resolution.

• New ClientErrorResponseException Class
  A new file, src/ClientErrorResponseException.php, has been added, which defines a distinct type of exception for "client errors". These are errors where the client sends a wrong or illegal request to the server.

• Update in InvalidResponseException Class Description
  The description of the InvalidResponseException class in src/InvalidResponseException.php was clarified to specify that it pertains to non-successful server response codes. This provides clearer understanding about its functionality and usage.

• Code Refinement in VKontakte
  In src/clients/VKontakte.php, an unnecessary use statement importing InvalidResponseException has been removed to streamline the code.

• New Test Method for sendRequest()
  A new test method, testSendRequest(), has been added in tests/BaseOAuthTest.php to validate the functionality of the revised sendRequest() method in varied scenarios. This enhances the overall test coverage and ensures the reliability of error handling changes.

[samdark]

Thanks.