chore(S3BasicFileAttributes): Do IO in methods that throw IOException

[guicamest]

Description of changes:

The implementation of S3BasicFileAttributes does IO whenever size(), lastModified() or fileKey() are invoked. When there are network problems, RuntimeExceptions are thrown, since the BasicFileAttributes nio interface does not declare any expected exceptions to be thrown when calling these methods.

In order to conform better with the contract specified by the nio interfaces, the IO done in size(), lastModified() and fileKey() methods is now done before constructing the attributes: when readAttributes from the provider or the attributeview is called. readAttributes in those interfaces specify that it can throw IOException and therefore seems a better place where to do the IO to get the object metadata.

As a side effect, requests to S3 are reduced whenever a user of a library needs more than 1 attribute of a file; for example size and lastModified.

References:

• BasicFileAttributes javadoc
• BasicFileAttributeView.readAttributes javadoc
• FileSystemProvider.readAttributes javadoc

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[markjschreiber]

Nice! Thanks