Release template_v2.1.0

[template_v2.1.0] 2024-05-06

Added

• Add support for the Aludel Elixir (aludel_elixir_ns) board.

Fixed

• Fix typo (app_sensors_read_and_steam → app_sensors_read_and_stream)
• Fix RPC registration error handling
• Fix an issue on boards using LTE connectivity where the Golioth Client was not
  started automatically (see
  #92 for details).

Changed

• Upgrade to Golioth Firmware SDK at v0.12.2
• Change app_sensors_init to app_sensors_set_client. On cellular boards,
  app_sensors_set_client is not guaranteed to run before
  app_sensors_read_and_stream, so any sensor initialization should moved to a
  separate function (e.g. app_sensors_init) that runs before
  app_sensors_read_and_stream.

Removed

• Remove unused click-i2c alias from nRF DK boards.