bq-paella: allow using newer WCNSS firmware from qcom-db410c

This allows bq-paella users to choose between the original stock WCNSS (WiFi/BT) firmware or the slightly newer version from qcom-db410c. By default the newer version from qcom-db410c is installed, but users can switch to the original (BQ) stock firmware by running apk add firmware-bq-picmt-wcnss.

Note: This depends on https://gitlab.com/postmarketOS/pmbootstrap/-/commit/3ebb994206fc8923aedf8f7c9c3299a3e746432f (not yet part of a pmbootstrap release) to install the correct firmware package by default. Without it, firmware-bq-picmt-wcnss will still be installed by default, not firmware-qcom-db410c-wcnss.

See commit log for detailed explanations of the changes.

Cc: @lazzardo