PageMatch: Return fetched content in match_data

[samford]

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This is a follow-up to #10113, which made modifications to PageMatch to support working with cached content, as a way of being able to modify the Xorg strategy to use PageMatch internally (like other strategies). With those changes, PageMatch properly works with page content that's passed to #find_versions.

However, the issue is that Xorg isn't actually able to cache page content in the current state because PageMatch isn't passing fetched content back to it in its return hash (match_data). Before #10113, I had been deleting the :content from match_data (as it wasn't necessary to keep it in the hash) and I simply forgot to modify that line when modifying PageMatch#find_versions to support cached content.

In general, this PR makes the following changes:

• Modify PageMatch#find_versions to return fetched page content in the match_data hash (i.e., not actively deleting it like we have been doing).
• Modify the condition where we check for provided_content in PageMatch#find_versions to ensure that provided_content is a string before using it.
• Set match_data[:cached] = true when PageMatch#find_versions is using provided_content. In this case, Cached?: Yes is printed in the debug output and ["meta"]["cached"] is set to true in the verbose JSON output. I missed this issue before because it's sometimes hard to tell when caching is actually working, so it's a good idea to surface this information.

Though I know it's the holidays, I'm labeling this "critical" so this fix can be integrated if anyone happens to review it over the next few days.

[BrewTestBot]

Review period will end on 2020-12-28 at 03:22:57 UTC.

[BrewTestBot]

Review period ended.

[MikeMcQuaid]

Thanks @samford!