* Use std::string for get_device_*_string helpers
Removes need to use BufferOwningPtr to avoid memory leaks.
* Rename get_device_info to get_device_info_string
Makes it more obvious that it should only be called for device queries
that return strings.
* Tokenize extensions in is_extension_available
Avoids the potential issue where one extension name is a prefix of
another.
* Throw exception when device info size is 0
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