Merge branch 'amiranda/119-add-a-user-level-library-for-functionalities-not-requiring-direct-scord-intervention' into 'main'

Resolve "Add a user level library for functionalities not requiring direct `scord` intervention"

This MR adds the library `libscord-user.so` with user-level interfaces to request
data transfers from `scord` from application code.

Closes #119

See merge request !103

Resolve "Tests require `scord.conf` to exist in `/etc`"

Closes #145

See merge request !102

Resolve "Update Spack"

This MR fixes an issue with conflicting CMake versions between `agio` and `scord` recipes.

It also adds a new `address` variant to enable configuring the binding address during installation with Spack.

Closes #144

See merge request !101

Add support for running tests while installing.

Resolve "Install `ping` client as utility binary"

Closes #138

See merge request !97

Fixes #138

Merge branch 'amiranda/142-rpc-servers-should-print-their-connection-address-as-returned-by-thallium' into 'main'

Resolve "RPC servers should print their connection address as returned by thallium"

Closes #142

See merge request !100

Resolve "Allow `scord-ctl` to write a pidfile"

Closes #141

See merge request !99

Resolve "Missing public interfaces for `ADM_node_t`"

Closes #140

See merge request !98

- Add `ADM_node_get_hostname()`
- Add `ADM_node_get_type()`

Resolve "`scord-ctl` binary is not installed"

Closes #139

See merge request !96

Fixes #139

Resolve "Use configured scripts for adhoc deployment/teardown"

This MR updates the deployment and termination RPCs so that they are
executed by `scord-ctl`. The mechanism takes advantage of the 
configuration information added in !93 to generate generic commands
for each configured adhoc storage instance.

This MR also updates `ADM_register_adhoc_storage`, making it generate
and record an internal `adhoc_uuid` that can be forwarded to `scord-ctl`
to refer to running adhoc storage instances.

This MR also renames the RPC `ADM_tear_down_adhoc_storage` to
`ADM_terminate_adhoc_storage`.

Closes #133

See merge request !94

- Rename `ADM_tear_down_adhoc_storage` RPC and related functions to
  `ADM_terminate_adhoc_storage`.
- scord-ctl: The new implementation for the RPC handler makes use of the
  new configuration files to construct the command line for termination.

- 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()`.