dogfooding: run scalafixAll with local scalafix-interfaces

[bjaglin]

This adds a command to replace the scalafix-interfaces brought in by sbt-scalafix with the local one. Rationale: observe impact of changes & detect regressions.

The implementation is not great as it's slow and mutates state, but I ran into dead-ends for the 2 alternatives I explored:

• injecting a custom scalafix-interfaces.properties to force the default scalafix-interfaces to load a custom scalafix-cli would require changes in the classloading logic to favor the custom property file over the one embedded in the JAR
• sbt-scalafix's scalafixInterfacesProvider could be rewired to cli2_12/fullClasspath with some minor addition, but it would require turning scalafixInterfacesProvider into a task key, which is not possible because the parser's completion can only depend on setting keys

[bjaglin]

this pollutes a bit the history locally, but it shouldn't hurt (and I can't think of a way to trigger the main project's command without the reload below anyway)

sbt:project> show dependencyOverrides
[info] * org.scala-sbt:scripted-plugin:1.8.3
[info] * ch.epfl.scala:scalafix-interfaces:0.11.0+10-1a516a0c+20230611-2036-SNAPSHOT
[info] * ch.epfl.scala:scalafix-interfaces:0.11.0+10-1a516a0c+20230611-2037-SNAPSHOT
[info] * ch.epfl.scala:scalafix-interfaces:0.11.0+10-1a516a0c+20230611-2038-SNAPSHOT
[info] * ch.epfl.scala:scalafix-interfaces:0.11.0+11-61c0c9e4+20230611-2100-SNAPSHOT
[info] * ch.epfl.scala:scalafix-interfaces:0.11.0+15-54c3f8dd+20230611-2111-SNAPSHOT
[info] * ch.epfl.scala:scalafix-interfaces:0.11.0+15-ee65ae33+20230611-2113-SNAPSHOT
[info] * ch.epfl.scala:scalafix-interfaces:0.11.0+15-e1c41e9f+20230611-2116-SNAPSHOT