Anjay 3.9.0

Features

• LwM2M Gateway functionality was added. To see the feature description, API
  documentation and tutorial on its usage, see Anjay docs
• Added a coap_downloader_retry_count and coap_downloader_retry_delay
  configuration options that allow to resume the CoAP download process in case
  of network errors.

Improvements

• Extended the functionality of the flag enabling Connection ID to also include
  connections to the file download CoAP server, in addition to the LwM2M server
• Migrated GitHub Actions tests on macOS to the macos-14 runner.
• Refactored test_ghactions.py.
• Added Github Actions test on macOS for the AppleClang.

Bugfixes

• Ensured that Github Actions tests on macOS actually runs on LLVM installed
  from Homebrew instead of AppleClang.
• Minor fix in the devconfig.