Read an argument and an image name without rewrite-docker internals

[timtebeek]

• Docker: revert rewrite-docker to its state before #8583 rewrite#8636 reverts rewrite-docker to its state before #8583, taking org.openrewrite.docker.internal.ArgumentContents and org.openrewrite.docker.trait.ImageName with it. UpgradeDockerImageVersion imports both, so main stops compiling the moment a snapshot carrying that revert lands. It merged this morning as 63b15b0b07, and this recipe is the only thing in this repository that touches rewrite-docker.

• Both classes were thin. text, textWithVariables and containsVariable walk an argument's contents, and only getPath() and getRegistry() of ImageName were ever read, so they move into the recipe as private helpers, registry detection rule and all. Nothing else the recipe reaches for moves in the revert: the tree types, Docker.File.getGlobalArgs() and DockerFrom's getImageName, getTag, withImageReference and withTag all predate #8583.

• That also finishes what Upgrade ARG default values used in Docker FROM instructions (hold for rewrite release) #1216 started. The recipe now links against no internal package and no trait helper, so the Moderne CLI classloader split that Revert "Upgrade ARG default values used in Docker FROM instructions" #1215 came from has nothing left to split on.

Two things the reverted grammar no longer does needed answering:

• An ARG default value's quotes sit inside the text of its literal rather than in the literal's quote style, so ARG JAVA_VERSION="11" read back as "11" and matched no version. They are taken off on read and put back on write, both no-ops against a version that models the quotes, so this holds either way.
• FROM eclipse-temurin: no longer round-trips, printing as FROM eclipse-temurin and failing the parser's own idempotency check. That is upstream and unrelated to this recipe, so the case leaves the no-change rows.

Verified against openrewrite/rewrite at 63b15b0b07, built and published locally: all 78 tests of UpgradeDockerImageVersionTest pass.

Reverting this

• These changes can be reverted once Docker: grammar rework, image reference traits, stage graph and BuildKit lint fixes rewrite#8637 is reviewed and merged, which reintroduces the grammar rework, ArgumentContents and the image reference traits the revert took out. The ARG quote handling stays correct against that tree rather than merely harmless, so the only thing genuinely waiting on #8637 is the FROM eclipse-temurin: no-change row.