Add db:truncate command with TestUtils helper

[Julien-R44]

• Fix a raising exception in Dialect.truncate when truncating a table whose name was reserved ( postgres / redshift )
• Add a command ace db:truncate which will truncate all tables, except those of Adonis that manage migrations
• Add aTestUtils().db().truncate() helper which is an alternative to TestUtils().db().migrate()

TestUtils.migrate() will migrate and rollback the whole database at each new run. So this is not necessarily necessary in most cases.

This new helper can be used as an alternative. What it will do is, apply the migrations at the beginning of the cycle, only if necessary, and at the end of the cycle, truncate all the tables.

[Julien-R44]

Should be good now

[thetutlage]

Looks beautiful 👍