Resolve "Prepare release 0.2.0"

Closes #112

See merge request !76

Resolve "Use mochi-thallium instead of our custom Margo engine"

This MR removes our in-house C++ engine for Margo and replaces it with 
mochi-thallium. This makes code simpler since the daemon implementation can 
be fully in C++, which prevents having to muck with C types and their 
lifetimes.

Closes #109

See merge request !74

Resolve "Use C++20"

Closes #108

See merge request !73

Merge branch 'amiranda/102-refactor-library-rpc-implementation-of-admire-remove_pfs_storage' into 'main'

Resolve "Refactor library RPC implementation of `admire::remove_pfs_storage`"

Closes #102

See merge request !71

Merge branch 'amiranda/101-refactor-library-rpc-implementation-of-admire-update_pfs_storage' into 'main'

Resolve "Refactor library RPC implementation of `admire::update_pfs_storage`"

Closes #101

See merge request !70

Merge branch 'amiranda/104-build-breaks-due-to-missing-tl-expected-commit-job-failed-30188' into 'main'

Resolve "Build breaks due to missing `tl::expected` commit (Job Failed #30188)"

Closes #104

See merge request !72

Fixes #104

Resolve "Refactor RPC implementation of `admire::register_pfs_storage`"

This MR moves the implementation of the RPC construction for
`ADM_register_pfs_storage` to `admire::detail` in `impl.[ch]pp`
similarly to other RPCs already refactored. This includes changing
the C ADM_types to native C++ types.

Closes #99

See merge request !68