Introduces a conanfile.py (and a Conan recipe for RocksDB) to enable building the package with Conan, choosing more recent default versions of dependencies. It removes almost all of the CMake build files related to dependencies, and the configurations for Travis CI and GitLab CI. A new set of cross-platform build instructions are written in BUILD.md.
Includes example GitHub Actions workflow for each of Linux, macOS, Windows.
* Test on macos-12
We use the <concepts> library which was not added to Apple Clang until
version 13.1.6. The default Clang on macos-11 (the sometimes current
version of macos-latest) is 13.0.0, and the default Clang on macos-12 is
14.0.0.
Closes#4223.
* Add a new operating mode to rippled called reporting mode
* Add ETL mechanism for a reporting node to extract data from a p2p node
* Add new gRPC methods to faciliate ETL
* Use Postgres in place of SQLite in reporting mode
* Add Cassandra as a nodestore option
* Update logic of RPC handlers when running in reporting mode
* Add ability to forward RPCs to a p2p node
