[PMM] Force Disconnect PMM from Platform

User Impact:
PMM admin user has not permissions to disconnect pmm from portal which complicates the troubleshooting when connection was done not properly.

Preconditions:

1. Log in to PMM as admin user
2. Create portal account and organization
3. Connect pmmPMMto the Platform using personal account credentials

Steps to reproduce:

1. Login to PMM server as PMM-admin user
2. Click on the Disconnect button to disconnect PMM from portal

Actual result:
Disconnect not allowed for pmm-admin users - Failed to get access token. Please sign in using the Percona account.

Expected result:
PMM-admin user has an option for force disconnecting PMM-server from the Platform. This will perform some clean-up for the existing connected PMM and reset the configuration.

Details:
Once a PMM server is connected to the platform with a percona account, we should be careful who is allowed to disconnect the PMM server.  There is currently a technical limitation that the logged-in user must be a percona account.  for clarity we will talk about 2 3 different permissions: 

• PMM Role (in PMM:  viewer or admin). Physical user. Example: admin/admin  = Admin 
• Platform Organization Role (in the portal, Org admin, Technical User). Example: [email protected] = Technical User 

 The following two scenarios should allow a user to sever the connection to the platform in order of what is currently capable:

1. The user currently logged into PMM with a Percona Account with the Platform Org Role of Org Admin: Should be able to disconnect PMM from the Portal.
2. An administrative override (in the event of being unable to communicate with portal) of PMM Role: Admin should be able to disconnect PMM from Portal. ( this is not currently possible due to the need for a token but we must take into account an organization's inability to get a token but still needing to disconnect.   Need to be done together  with SAAS-899) 

Any user logged in that does not meet 1, 2 should see a text tip describing who and how to disconnect. "You do not have permission to disconnect from the platform.  You need to be 1) logged in with a Percona Account and 2) your Percona Account must be granted Organization Admin"

If user uses option (2) - we need to warn them "You need also to disconnect PMM from the Portal at  ...  [LINK to  Portal page ]" 

Out of scope:
Portal disconnect flow