Client now reads host file to determine auto_sm and RPC protocol

gkfs::hg_tag -> gkfs::rpc::tag
gkfs::utils -> gkfs::util
gkfs::client -> gkfs::util
gkfs::logging -> gkfs::log

Reformatted code w.r.t. unifying code styles as of the official
CPPCoreGuidelines by Stroustrup and Sutter

Restructuring code w.r.t. configurations and definitions:
- #defines have been mostly removed from configurations
- a dedicated config file has been added for configurations with constexpr
- past configure file is now only a cmake wrapper
- wrapping global functions into namespaces

Removed all adafs and ifs occurrences. Now called gkfs

Fixes an issue where client applications such as ssh might attempt to
close all open fds, therefore also closing the fds used by the internal
components of the library such as Mercury.

If we intercept function during shutdown we could try to access the
internal file map that has been already freed.

This woun't affect performance at runtime since we are always checking
only one boolean flags on every interception as before.

On the other hand should sppedup the shutdown of the library, because we
disable the interception of glibc library call before performing the
shutdown routines.

when resolving path we don't want always
to resolve also the last components if it is a link. Cause in some cases
we want exactly the path of that link and not the one it points to.

lstat and readlink are some example of functions that don't want to
resolve the last link.

relativize path now accepts a file descriptor.

If fd is AT_FDCWD relative path need to be considered with respect to
the current working directory. Otherwise the path is relative to the
directory with the given file descriptor

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