Backport NODE-3998 to v4.x.

Parent Ticket Description:

What problem are you facing?

The platform field of the client metadata is being set to:
"Node.js v16.13.0, LE (unified)|Node.js v16.13.0, LE (unified)"
the text after the vertical bar is supposed to be text from a driver wrapper or other custom driverInfo settings.

What driver and relevant dependency versions are you using?

Steps to reproduce?

connect a 4.x client to mongod and inspect the connection logs.

Acceptance Criteria

• Prevent many calls to makeClientMetadata from duplicating the platform string
• Refactor initial handshake generation.
• Add unit testing to cover makeClientMetadata
• Test that driverInfo options are appended only once
  • Users can provide driverInfo name, version, and platform, which should be appended to the Node.js results of those properties separated by a bar character '|'
  • Example: If I pass this driverInfo option into the MongoClient

    { driverInfo: { platform: 'myPlatform', name: 'myName', version: 'myVersion' } } 
    

    the metadata should have:

    {
      driver: { name: 'nodejs|myName', version: '4.7.0|myVersion' }
      platform: 'Node.js v16.13.0, LE (unified)|myPlatform' 
    }
    

    Each property (name, version, platform) is optional in driverInfo, we only append '|' + user data if passed a non-empty string.

• Assert the results always have the following shape: (See linked reference slides)

  {
    driver: { 
      name: 'nodejs', 
      version: '4.7.0' 
    },
    os: {
      type: 'Darwin',
      name: 'darwin',
      architecture: 'x64',
      version: '21.5.0'
    },
    platform: 'Node.js v16.13.0, LE (unified)'
  }