This PR moves some AST transforms, those that are used both by the v1 and v2 parsers, into nf-lang.

This is needed to give me better visibility and control over the total sequence of AST transforms in the Nextflow compiler. It also allows me to remove some ugliness in ScriptCompiler and ConfigCompiler.

I left some AST transforms like NextflowDSLImpl alone because they aren't used by the v2 parser and will be deprecated anyway.

Copilot summary

This pull request refactors the AST transformation logic in the Nextflow codebase by replacing several standalone implementation classes with inline implementations defined within their respective annotations. Additionally, it removes unused imports and simplifies the structure of transformation-related files. The changes also include the migration of the LangHelpers utility class to a new package to better align with its purpose. Below are the key changes grouped by theme:

Refactoring AST Transformations:

• Replaced the standalone NextflowXformImpl class with an inline implementation inside the NextflowXform annotation. The new implementation uses PathCompareVisitor for path comparison logic. (modules/nextflow/src/main/groovy/nextflow/ast/NextflowXform.groovy)
• Replaced the standalone OpXformImpl class with an inline implementation inside the OpXform annotation, utilizing OpCriteriaVisitor for transforming closure arguments into criteria objects. (modules/nextflow/src/main/groovy/nextflow/ast/OpXform.groovy)
• Replaced the standalone TaskTemplateVarsXformImpl class with an inline implementation inside the TaskTemplateVarsXform annotation, delegating variable capture to TaskTemplateVisitor. (modules/nextflow/src/main/groovy/nextflow/ast/TaskTemplateVarsXform.groovy)
• Replaced the standalone StripSecretsXformImpl class with an inline implementation inside the StripSecretsXform annotation, using StripSecretsVisitor to handle secret property replacements. (modules/nextflow/src/main/groovy/nextflow/config/StripSecretsXform.groovy) [1] [2]

Code Cleanup:

• Removed the now-unused standalone implementation files: NextflowXformImpl.groovy, OpXformImpl.groovy, TaskTemplateVarsXformImpl.groovy, and StripSecretsXformImpl.groovy. [1] [2] [3]
• Eliminated unused imports from Nextflow.groovy, ConfigCompiler.java, and ScriptCompiler.java after removing the standalone transformation implementations. [1] [2] [3]

Compiler Updates:

• Updated the ConfigCompiler and ScriptCompiler classes to use the new visitor-based transformation approach (PathCompareVisitor, OpCriteriaVisitor, and StripSecretsVisitor) instead of the removed standalone classes. (modules/nextflow/src/main/groovy/nextflow/config/parser/v2/ConfigCompiler.java) [1] [2]

Utility Class Migration:

• Moved the LangHelpers class from the nextflow.ast package to nextflow.util to better reflect its utility nature. Adjusted its visibility by removing the @PackageScope annotation. (modules/nextflow/src/main/groovy/nextflow/util/LangHelpers.java) [1] [2] [3] [4]