- scord-ctl: The new implementation for the RPC handler makes use of
  the new configuration files to construct the command line for
  deployment. The RPC handler will now reply with the generated path
  for the adhoc storage system (`adhoc_dir`) in addition to an
  appropriate error code.

- scord: The RPC handler has been refactored and will now propagate
  `adhoc_dir` to the client API.

- API: The newly generated `adhoc_dir` is propagated to client code.

- examples: Updated to account for the new `adhoc_storage_path` argument in
  the APIs.

foo

- Move as much code as possible to `logger.cpp`
- Create `logger_base` with common code
- Create `logger_sync` and `logger_async` classes to allow creating
  synchronous and asynchronous loggers as needed.
- Replace all mentions to `global_logger` by `default_logger`

Resolve "Adhoc storage deployment needs to be refactored"

This MR implements a generic mechanism for deploying adhoc storage
systems in `scord-ctl`. The mechanism allows users to define via
the `scord-ctl.conf` configuration file which scripts should be 
used to start and stop an adhoc storage system.

Closes #116

See merge request !93

- Reason: There are issues with `std::ranges` implementation in
clang-10, clang-11, and clang-12 (at least).

- Refactor `eval()`: The function now returns a new `command` instance.
- Add `as_vector()`: This function splits the command line by ' ' and
returns it as a vector of strings.

- Implement `environment::as_vector()`.
- Add `environment::size()`.

Merge branch 'amiranda/115-adhoc-storage-deployment-needs-to-be-executed-by-scord-ctl-instead-of-scord' into 'main'

Resolve "Adhoc storage deployment needs to be executed by `scord-ctl` instead of `scord`"

Closes #115

See merge request !92

`scord` now just forwards the request to the appropriate `scord-ctl`
instance.

- Add `endpoint lookup(std::string address)` so that a RPC server can
lookup peers for RPC forwarding.
- Add `std::string self_address()` so that a RPC server can determine
its own address string.

Our network interface now relies on Thallium's support for `providers`
(https://mochi.readthedocs.io/en/latest/thallium/09_providers.html).
This allows using the member functions from a class as RPC handlers,
which in turn allows RPC handers to access the class' data members.

Thus, we have heavily refactored `scord`:

- Create a new `scord::rpc_server` class that inherits both from
`network::server` and `network::provider`. This enables the
aforementioned functionality.
- The RPC handlers for `scord` are now member functions of
`scord::rpc_server` instead of free functions.
- The managers used by `scord` (i.e. the `job_manager`,
`adhoc_storage_manager`, and `pfs_storage_manager` are now members of
`scord::rpc_server` instead of singletons, since they no longer need to
be accessed globally.

Similarly for `scord-ctl`:
- Create a new `scord_ctl::rpc_server` class that inherits both from
`network::server` and `network::provider`. This enables the
aforementioned functionality.
- The RPC handlers for `scord-ctl` are now member functions of
`scord_ctl::rpc_server` instead of free functions.

Additionally, we have also moved the `network` and `logger` namespaces
outside of `scord`, since this code is shared by both `scord` and
`scord-ctl`.

Update tests to start scord-ctl as needed

Fixes #129

Fixes #128

Resolve "Refactor CLI for scord and scord-ctl"

Closes #127

See merge request !91

scord:
- Configuration file now uses standard YAML format
- Add `--output` CLI argument (SCORD_LOG_OUTPUT)

scord-ctl:
- Add `--output` CLI argument
- Add `--listen` CLI argument (Fixes #126)
- Remove configuration file

Both:
- Remove file_options dependency
- Remove genopts dependency
- Replace yaml-cpp with rapidyaml
- Replace general settings with specific configurations (fixes #20)
- General improvements and bugfixes in `logger`
- Improved `net::server` configuration
- Fix fork()-related bug in `signal_listener`
- Remove environment variables

"Resolve build fails with outdated `tl::expected`"

See merge request !89

Fixes #125

Merge branch 'amiranda/93-api-offers-no-way-to-tear-down-an-adhoc-storage-system-after-it-has-been-deployed' into 'main'

Resolve "API offers no way to tear down an adhoc storage system after it has been deployed"

Closes #93

See merge request !87