Make all features explicit (#6267)

* make all features explicit

* Change to -feature suffix to with- prefix

* Add newline at the end of the Cargo.toml file

* Remove rhd feature

* Remove some features from Cargo.toml

* Remove test-helpers feature in tx pool

* Return db_open_error("with-"..

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Rename subdb feature to with-subdb

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Remove 'strict' feature and cfg_attr

* Check for with-subdb feature instead of subdb

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>