Make the login call-to-action clearer

# GWA-CLI Issue

## Priority: Medium/High
## Issue Type: Feature

## User Story

**As an** API Provider,
**I want** to successfully login through the `gwa CLI` using my IDIR credentials,
**so that** I can configure Gateway services.

**Current Login Flow**
The current flow of the `gwa login` command is unclear especially, the phrase "authentication handshake" has caused confusion, and users are often unsure of what actions they need to take. This results in delays and failed login attempts.

The prompt currently reads:
```
Please sign in at https://authz-apps-gov-bc-ca.test.api.gov.bc.ca/auth/realms/aps/device
Input the following code GOVJ-HSMF

Waiting for authentication handshake...
```

**Proposed New Message Flow:**
The message should be updated to something more user-friendly, like:
```
Please open the following URL in your browser to complete the login process:
https://authz-apps-gov-bc-ca.test.api.gov.bc.ca/auth/realms/aps/device

Enter the following code on the web page when prompted: GOVJ-HSMF

Once you have successfully logged in, return to this terminal to complete the authentication process.
```

## Acceptance Criteria

- The `gwa login` command should display clear and concise instructions for the login process.
- Users should be instructed to open the provided URL in their browser.
- Users should be instructed to input the provided code on the website.
- Messaging should include guidance for users to return to the terminal after completing the login.
- Ensure that the new messaging is tested and works for all supported platforms.

Start at the `gwa login` command and locate where its device-login prompt and `Waiting for authentication handshake...` message are assembled. Update the instructions to cover opening the URL, entering the code, and returning to the terminal, then verify the output and supported-platform behavior with the login tests or command checks available in the repository.

Written by the indexing model from the issue text.