Instead of using the more complex adafs_pread function now is possible
to use adafs_read when it is necessary to read starting from the current
file position

Fix typo

when size is 0 the buffer to host the path of CWD must be allocated by
us

Always store complete path as CWD instead of internal and relative ones

`tar` and other gnu coreutils are using __openat{64,}_2 variant.
We need to intercept also that apart of the main `openat` function.

StackOverflow related question [1]

[1]: https://stackoverflow.com/questions/9161116/intercepting-the-openat-system-call-for-gnu-tar

add support for path resolution, this will be used to get canonical path.

More info at `man path_resolution`

During interception library startup the CWD of intercepted process is
stored in the PreloadContext object

Metadata refactoring

See merge request zdvresearch_bsc/adafs!93

Metadata class needs to be used by both the client and the daemon

The metadata class needs to represent metadata of a file,
thus it shouldn't contain the path itself. In fact we actually didn't
use it at all.

This will make further refactoring easier and it save some memory copies.

avoid construction of intermediate string when prepending the separator

Fix IO on directories

See merge request zdvresearch_bsc/adafs!92

towards path resolution

Closes #52

See merge request zdvresearch_bsc/adafs!88

Also tested with benchmark test tool.

This allowed to avoid improper static_cast to check downcasting

changelog for the new version:
https://github.com/facebook/rocksdb/releases/tag/v5.15.10