Expected end of experiment messages

[mfendeksilverstripe]

Description

Each experiment has content of start, duration and the expected end. We should improve how this information in surfaced:

• add a label to indicate the end of experiment data time
• stop redirections after that date (both in terms of render but also cached pages - in JS)

Additional context or points of discussion

No response

Validations

• You intend to implement the feature yourself
• You have read the contributing guide
• You strongly believe this feature should be in core, rather than being its own community module
• You have checked for existing issues or pull requests related to this feature (and didn't find any)