Adds support to run Cypress test in an ODFE cluster with security enabled

[ftianli-amzn]

Issue #, if available:

Description of changes:

• Add an environment variable security_enabled to mark if security feature is enabled in the ODFE cluster.
  When security_enabled is true:

1. Switch the base URL for Elasticsearch to https://localhost:9200
2. Overwrite cy.visit() and cy.request() to add a basic authentication header (admin:admin) into the http requests.

• Change the way of clean-up used for the test from deleting all indices to only delete monitors or destinations, mainly because admin user doesn't have permission to delete system indices
• Add custom Cypress commands for deleteMonitorByName, deleteAllMonitors, deleteAllDestinations, createIndexByName, deleteIndexByName and insertDocumentToIndex
• Change the test implementations about "alert", due to alert history can not be removed by admin user.
  A noticeable change is adding a unique number in the monitor names to filter the desired alert out.
• Add an assertion before clearing all the text in input textfield, because when text in textfields is too long, the removing operation can't wait for the text loading and results in uncompleted removing.

Usage:
The environment variable security_enabled is set to false by default.
Appending --env security_enabled=true to the cypress command to change the value, other ways to set the environment variable please refers to the link.

Reference: opendistro-for-elasticsearch/anomaly-detection-kibana-plugin@455e3f8

Result for running cypress run --env security_enabled=true in an ODFE cluster with security enabled:

       Spec                                              Tests  Passing  Failing  Pending  Skipped  
  ┌────────────────────────────────────────────────────────────────────────────────────────────────┐
  │ ✔  alert_spec.js                            02:30        5        5        -        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✔  destination_spec.js                      00:30        4        4        -        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✔  monitor_spec.js                          00:40        6        6        -        -        - │
  └────────────────────────────────────────────────────────────────────────────────────────────────┘
    ✔  All specs passed!                        03:42       15       15        -        -        -  

Result for running cypress run in an Elasticsearch cluster with only Alerting plugin:

       Spec                                              Tests  Passing  Failing  Pending  Skipped  
  ┌────────────────────────────────────────────────────────────────────────────────────────────────┐
  │ ✔  alert_spec.js                            02:24        5        5        -        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✔  destination_spec.js                      00:29        4        4        -        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✔  monitor_spec.js                          00:26        6        6        -        -        - │
  └────────────────────────────────────────────────────────────────────────────────────────────────┘
    ✔  All specs passed!                        03:20       15       15        -        -        -  

Result for running yarn test:jest

Test Suites: 6 skipped, 83 passed, 83 of 89 total
Tests:       20 skipped, 385 passed, 405 total
Snapshots:   135 passed, 135 total
Time:        61.195 s
Ran all test suites.
✨  Done in 62.55s.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[ftianli-amzn]

The latest successful workflow run: https://github.com/opendistro-for-elasticsearch/alerting-kibana-plugin/actions/runs/484258034
(Can also be accessed from the ✅ on above commit.)