In unzip_file(), confirm we have enough available disk space before extracting.

"enough" is calculated by adding up the uncompressed size of the files in the archive, then adding a 20% buffer.

props dd32.
fixes #25576.

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git-svn-id: http://core.svn.wordpress.org/trunk@25687 1a063a9b-81f0-0310-95a4-ce76da25c4cd
In the upgrader, only print additional error data if it is a string.

As in [25576], we sometimes want to return additional data that is not necessarily meant for UI consumption.

see #25576.

Built from https://develop.svn.wordpress.org/trunk@25775


git-svn-id: http://core.svn.wordpress.org/trunk@25688 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Account for possible failures by disk_free_space(), as well as the potential need to copy the unzipped files.

see #25576.

Built from https://develop.svn.wordpress.org/trunk@25776


git-svn-id: http://core.svn.wordpress.org/trunk@25689 1a063a9b-81f0-0310-95a4-ce76da25c4cd