This is part 1 of 4 for renaming the `newdbplugin` package. This copies the existing package to the new location but keeps the current one in place so we can migrate the existing references over more easily.

* Switch to go modules

* Make fmt

* Database updates

* Add create/update distinction for connection config
* Add create/update distinction for role config
* Add db name and revocation statements to leases to give revocation a
shot at working if the role has been deleted

Fixes #3544
Fixes #4782

* Add create/update info to docs

* prevent returning password in reads of connection config info

* fixing a test

* masking password in connection url on reads

* addressing feedback

* removing extra check

* Remove sensitive fields when reading config data

* Do not use structs; build and return map explicitly

* Revert tag in postgresql

* Fix tests

* redoing connection handling

* a little more cleanup

* empty implementation of rotation

* updating rotate signature

* signature update

* updating interfaces again :(

* changing back to interface

* adding templated url support and rotation for postgres

* adding correct username

* return updates

* updating statements to be a list

* adding error sanitizing middleware

* fixing log sanitizier

* adding postgres rotate test

* removing conf from rotate

* adding rotate command

* adding mysql rotate

* finishing up the endpoint in the db backend for rotate

* no more structs, just store raw config

* fixing tests

* adding db instance lock

* adding support for statement list in cassandra

* wip redoing interface to support BC

* adding falllback for Initialize implementation

* adding backwards compat for statements

* fix tests

* fix more tests

* fixing up tests, switching to new fields in statements

* fixing more tests

* adding mssql and mysql

* wrapping all the things in middleware, implementing templating for mongodb

* wrapping all db servers with error santizer

* fixing test

* store the name with the db instance

* adding rotate to cassandra

* adding compatibility translation to both server and plugin

* reordering a few things

* store the name with the db instance

* reordering

* adding a few more tests

* switch secret values from slice to map

* addressing some feedback

* reinstate execute plugin after resetting connection

* set database connection to closed

* switching secret values func to map[string]interface for potential future uses

* addressing feedback

* Start work on passing context to backends

* More work on passing context

* Unindent logical system

* Unindent token store

* Unindent passthrough

* Unindent cubbyhole

* Fix tests

* use requestContext in rollback and expiration managers

* Start work on context aware backends

* Start work on moving the database plugins to gRPC in order to pass context

* Add context to builtin database plugins

* use byte slice instead of string

* Context all the things

* Move proto messages to the dbplugin package

* Add a grpc mechanism for running backend plugins

* Serve the GRPC plugin

* Add backwards compatibility to the database plugins

* Remove backend plugin changes

* Remove backend plugin changes

* Cleanup the transport implementations

* If grpc connection is in an unexpected state restart the plugin

* Fix tests

* Fix tests

* Remove context from the request object, replace it with context.TODO

* Add a test to verify netRPC plugins still work

* Remove unused mapstructure call

* Code review fixes

* Code review fixes

* Code review fixes

Fixes #2823

* WIP on invalidate function

* cassandraConnectionProducer has Close()

* Delete database from connections map on successful db.Close()

* Move clear connection into its own func

* Use const for database config path