[ML] Rename client side privileges to capabilities where applicable.

[jgowdyelastic]

The /api/ml/ml_capabilities endpoint provides a list of abilities the user has as capabilities, however when stored on the client side it is renamed to privileges. This was to avoid a large amount of code churn when implementing #39749

A follow up PR is needed to bring the client side code up to date with this wording.

for reference, the response from /api/ml/ml_capabilities :

{
  "capabilities": {
    "canGetJobs": false,
    "canCreateJob": false,
    "canDeleteJob": false,
    "canOpenJob": false,
    "canCloseJob": false,
    "canForecastJob": false,
    "canGetDatafeeds": false,
    "canStartStopDatafeed": false,
    "canUpdateJob": false,
    "canUpdateDatafeed": false,
    "canPreviewDatafeed": false,
    "canGetCalendars": false,
    "canCreateCalendar": false,
    "canDeleteCalendar": false,
    "canGetFilters": false,
    "canCreateFilter": false,
    "canDeleteFilter": false,
    "canFindFileStructure": true,
    "canGetDataFrame": true,
    "canDeleteDataFrame": true,
    "canPreviewDataFrame": true,
    "canCreateDataFrame": true,
    "canStartStopDataFrame": true
  },
  "upgradeInProgress": false,
  "isPlatinumOrTrialLicense": false,
  "mlFeatureEnabledInSpace": true
}

[elasticmachine]

Pinging @elastic/ml-ui

[peteharverson]

Closing as fixed for 7.8.0 by #64057