feat: (Core) add semantic icons to Message box and remove the close button

[InnaAtanasova]

Please provide a link to the associated issue.

Closes #3887

Please provide a brief summary of this pull request.

• introduced semantic icons into Message box component
• removed the close button as per Fiori specs
• the Switch component is broken but it comes from v.0.14.0 of Fundamental-styles and is fixed in this PR

BREAKING CHANGE:
MessageBoxCloseIconComponent component is removed

Please check whether the PR fulfills the following requirements

• the commit message follows the guideline:
  https://github.com/SAP/fundamental-ngx/blob/master/CONTRIBUTING.md
• tests for the changes that have been done
• all items on the PR Review Checklist are addressed :
  https://github.com/SAP/fundamental-ngx/wiki/PR-Review-Checklist

Documentation checklist:

• update README.md
• Breaking Changes Wiki
• Documentation Examples
• Stackblitz works for all examples

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[InnaAtanasova]

NOTE: tests are failing for FlexibleColumnLayout but they are fixed in 2 other PRs (just need someone to review them :) )
#4108 and #4116

As mentioned in the template, Switch component is broken but it's due to v.0.14.0 which is fixed in #4116

[salarenko]

1. RIP close button. Do we have to remove this feature? It looks like it also should't be supported in the Dialog component, but we keep it there. It's weird that the design excluded such common element.
2. Should we force user to put the icon element in the header by himself? Maybe we could put it always in the default message-box header template and show the user how to compose it by himself in the " Complex template" example?