feat: [FC-0044] expose editor for advanced xblocks (#2528)

[monteri]

Description

Adding editor view on backend to embed it into Studio MFE in an Iframe

Supporting information

Link to other information about the change, such as Jira issues, GitHub issues, or Discourse discussions.
Be sure to check they are publicly readable, or if not, repeat the information here.

Testing instructions

• Go to - {CMS_BASE}/xblock/{xblock_locator}/editor

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[GlugovGrGlib]

Reopened in #34929

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@monteri Even though your pull request wasn’t merged, please take a moment to answer a two question survey so we can improve your experience in the future.