core_h5p: add renderer to let personalize styles (backport of MDL-69087)

"Testing Instructions" copied from  https://tracker.moodle.org/browse/MDL-69087 Setup Download the theme h5pmod to your local Moodle instance running the following command from the Moodle root folder:  git clone https://github.com/sarjona/h5pmods-moodle-plugin.git  theme/h5pmod   Login as admin. Run the upgrade process, to install the h5pmod theme. Access to "Site administration / Appearance / Themes / Theme selector" and choose "H5PMod" as Default theme. Go to the Content bank. Upload the attached H5P files to the content bank (interactive-video.h5p and multiple-choice.h5p).   Testing scenario 1: Interactive video - h5p_alter_styles and h5p_alter_scripts (player and editor) Open the browser console. Access to the "Interactive video" H5P entry from the content bank.  Confirm  the H5P slider bar is red. Confirm  the playbackRate control button (near the slider), is now green. Confirm  the following text appears in the JS console: "Hello, this is custom.js!". Go to the first interactive point ("Multiple choice quiz") and open it. Confirm  the "Check" button background is pink (look at the attached interactive_video_view.png). Click the "Edit" button, to access to the H5P editor. Confirm  the following text appears in the JS console: "Hello, this is customEditor.js!". Confirm  some of the headings, such as "Title" or "Add a video" has pink background  (look at the attached interactive_video_edit.png).   Testing scenario 2: Multiple choice - h5p_alter_semantics (editor) and h5p_alter_filtered_parameters (player) Open the browser console. Access to the "Multiple choice" H5P entry from the content bank.  Confirm  the "Generated at xxxxxxxxxxx"  text is displayed below the statement ("Question 1").  Look at the attached multiple_choice_view.png. Click the "Edit" button, to access to the H5P editor. Confirm  there is no any "Image" field between the Title and the Question (look at the attached multiple_choice_edit.png).   Testing scenario 3: Boost theme Access to "Site administration / Appearance / Themes / Theme selector" and choose "Boost" as Default theme. Go to the Content bank. Open the browser console. Access to the "Interactive video" H5P entry from the content bank.  Confirm  the H5P slider bar is not red anymore. Confirm  the playbackRate control button (near the slider), is not green anymore. Confirm  the following text doesn't appear in the JS console: "Hello, this is custom.js!". Go to the first interactive point ("Multiple choice quiz") and open it. Confirm  the "Check" button background is blue. Click the "Edit" button, to access to the H5P editor. Confirm  the following text doesn't appear in the JS console: "Hello, this is customEditor.js!". Confirm  the headings, such as "Title" or "Add a video", are not pink anymore. Access to the "Multiple choice" H5P entry from the content bank.  Confirm  the "Generated at xxxxxxxxxxx"  text is not displayed anymore. Click the "Edit" button, to access to the H5P editor. Confirm  there is an "Image" field between the Title and the Question in Media section.