\Drupal calls should be avoided in classes, use dependency injection instead

Problem/Motivation

FILE: ..._html_field/src/Plugin/Field/FieldFormatter/ReadonlyHtmlFieldFormatter.php
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FOUND 0 ERRORS AND 2 WARNINGS AFFECTING 2 LINES
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23 | WARNING | \Drupal calls should be avoided in classes, use dependency
| | injection instead
24 | WARNING | \Drupal calls should be avoided in classes, use dependency
| | injection instead
--------------------------------------------------------------------------------

FILE: ...adonly_html_field/src/Plugin/Field/FieldWidget/ReadonlyHtmlFieldWidget.php
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FOUND 0 ERRORS AND 4 WARNINGS AFFECTING 4 LINES
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24 | WARNING | \Drupal calls should be avoided in classes, use dependency
| | injection instead
25 | WARNING | \Drupal calls should be avoided in classes, use dependency
| | injection instead
38 | WARNING | \Drupal calls should be avoided in classes, use dependency
| | injection instead
39 | WARNING | \Drupal calls should be avoided in classes, use dependency
| | injection instead
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Time: 330ms; Memory: 10MB

Steps to reproduce

Execute the command: phpcs --standard=Drupal,DrupalPractice --extensions=php,module,inc,install,test,profile,theme,css,js,info,txt,md,yml,twig readonly_html_field/

Proposed resolution

Add dependency injection

Remaining tasks

Patch review.