Replace Go skip markers with config

[dagger-codex]

Summary

• replace skip marker filename configuration with top-level skipLint, skipTest, and skipGenerate path lists
• use the same skip path config for module discovery filters, all-module commands, and per-module skip introspection
• migrate e2e fixtures off marker files and remove the old sentinel files

Fixes #17

Schema diff

Human-readable schema changes:

type Go {
  new(
-   skipLintFilename: String! = ".dagger-skip-go-lint"
-   skipTestFilename: String! = ".dagger-skip-go-test"
-   skipGenerateFilename: String! = ".dagger-skip-go-generate"
+   skipLint: [String!]! = []
+   skipTest: [String!]! = []
+   skipGenerate: [String!]! = []
  )

- skipLintFilename: String!
- skipTestFilename: String!
- skipGenerateFilename: String!
+ skipLint: [String!]!
+ skipTest: [String!]!
+ skipGenerate: [String!]!
}

The per-module introspection methods keep their names and signatures, but now read from the top-level skip path config:

• GoModule.skipLint(ws: Workspace!): Boolean!
• GoModule.skipTest(ws: Workspace!): Boolean!
• GoModule.skipGenerate(ws: Workspace!): Boolean!

Full diff in this PR: https://github.com/dagger/go/pull/19/files

Tests

• dagger check -m .dagger/modules/e2e