Merge branch '78-errno-115-returned-on-successful-completion-for-several-system-calls' into 'master'

This fix contains three parts:

1. errno 115 was leaked during initialization of the client in
   init_ld_environment_(). However, the value on its own is irrelevant to
   this issue as all internal errno variable changes should be kept
   internal as it is the case during each syscall intercept hook.
   Therefore, the original errno variable is restored after the
   initialization finishes.
2. lseek() tests revealed that whence SEEK_SET was not handled
   correctly. It should not allow negative offsets.

3. All FIXME TODOs in the testing code have been removed including
   testing on the errno in a successful case because it is undefined.

Resolve "Errno 115 returned on successful completion for several system calls"

Closes #78

See merge request !65

Testing on an error code in the successful case has an undefined value
and was therefore removed.

This was previously causing an errno of 115 during tests. While an errno of 0 is not guaranteed on success, all errno's within GKFS should be kept internal.

This reverts merge request !64

Merge branch '119-new-options-auto_sm-and-rpc_protocol-should-use-dashes-as-separators' into 'master'

Resolve "New options `--auto_sm` and `--rpc_protocol` should use dashes as separators"

Closes #119

See merge request !63

Resolve "AGIOS should not be required in CMake"

Closes #118

See merge request !62

Resolve "Set RPC protocol and auto_sm at runtime and not compile time"

Closes #101 and #118

See merge request !40

Client now reads host file to determine auto_sm and RPC protocol

Resolve "Refactor readdir()"

Closes #117

See merge request !55

- more error handling
- removed runtime exception from client
- Streamlining error handling in client and making it consistent. Adding comments
- Improved readdir logging

Implementation of GekkoFWD, an I/O forwarding mode for GekkoFS using AGIOS for I/O request scheduling.

See merge request !44

data_integrity test remaining statx() to stat()

Closes #115

See merge request !59

Resolve "[daemon] chunk storage backend crashes the server on error"

Closes #75

The `ChunkStorage` backend class on the daemon was throwing `system_errors` without being caught, crashing the server in the process. `ChunkStorage` now uses a designated error class for errors that might occur. In addition the dependency to Argobots was removed which was used to trigger `ABT_eventuals`, laying ground work for future non-Argobots IO implementations. Further, the whole class was refactored for consistency and failure resistance.

A new class `ChunkOperation` is introduced which wraps Argobots' IO task operations which allows the removal of IO queue specific code within RPC handlers, i.e., read and write handlers. The idea is to separate eventuals, tasks and their arguments from handler logic into a designated class. Therefore, an object of an inherited class of `ChunkOperation` is instantiated within the handlers that drives all IO tasks. The corresponding code was added to the read and write RPC handlers. Note, `ChunkOperation` is not thread-safe and is supposed to be called by a single thread.

In addition, truncate was reworked for error handling (it crashed the server on error) and that it uses the IO queue as well since truncate causes a write operation and should not overtake IO tasks in the queue.

The chunk stat rpc handler was refactored for error handling and to use error codes as well. 

Further minor changes:
- dead chunk stat code has been removed
- some namespaces were missing: `gkfs::rpc`
- more flexible handler cleanup and response code
- fixed a bug where the chunk dir wasn't removed when the metadata didn't exist on the same node

Misc:
There was some discussion about putting the removal of the chunk directory into the IO queue as well with the same argument as truncate, but I refrain to do so as it would likely notably increase remove performance. I think, we can put this under *eventual consistency* and call it a day for now. Truncate was another story as glibc makes heavy use of truncate in various operations.

See merge request !32