[plg_system_cache] Disable gzip before caching the page

[SharkyKZ]

Pull Request for Issue #17501.

Summary of Changes

Makes sure we store uncompressed page in cache.

Testing Instructions

Enable Gzip Compression in Global Configuration.
Enable System - Page Cache plugin.
Open some cacheable frontend page with a form, e.g. username reminder page. Remember its URL.
Start a new session (e.g. clear browser session or use a different browser).
Open the same page and try to submit form.

Expected result

Form submitted.

Actual result

Submitting form fails with warning:

The security token did not match. The request was aborted to prevent any security breach. Please try again.

Documentation Changes Required

No.

[richard67]

Will the page from the cache be served zipped or unzipped?
Update: Looks as if the browser still gets the cached page compressed => good.

[richard67]

I have tested this item ✅ successfully on 6c8c523

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[viocassel]

I have tested this item ✅ successfully on 6c8c523

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[Quy]

RTC

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[HLeithner]

Thank you for fixing the cache.