Android: replace deprecated StatFs functions

[ath0mas]

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Platforms affected

Android

Motivation and Context

getAvailableBlocks and getBlockSize are deprecated since API 18

Description

getAvailableBytes is available since API 18 while current cordova-android must be >=12.0.0, so minSdk 24

Testing

Checklist

• [x] I've run the tests to see all new and existing tests pass
• [x] I added automated test coverage as appropriate for this change
• [x] Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• [x] If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• [x] I've updated the documentation if necessary