Implement the enhanced-parts feature

[eernstg]

This issue is used to track the implementation of the 'enhanced-parts' feature.

Feature specification: https://github.com/dart-lang/language/blob/main/working/augmentation-libraries/parts_with_imports.md.

Experiment flag: enhanced-parts.

Subtasks:

• [enhanced-parts] Write the spec #56190
• [enhanced-parts] Language tests #56191
• [enhanced-parts] Co19 tests - add tests #56192
• [enhanced-parts] Implement feature in the CFE #56193
• [enhanced-parts] Analyzer implementation #56194
• [enhanced-parts] Analysis server / IDE #56203
• [enhanced-parts] Tests validating as passing (Tracking via Google Sheet) #56195
• [enhanced-parts] Syntax highlighters implementation #56196
• [enhanced-parts] DDC implementation #56197
• [enhanced-parts] Dart2js implementation #56198
• [enhanced-parts] VM implementation #56199
• [enhanced-parts] Build system support #56200
• [enhanced-parts] Web debugging support #56201
• [enhanced-parts] Core library updates #56202
• [enhanced-parts] dart_style support #56204
• [enhanced-parts] dartdoc implementation #56205
• [enhanced-parts] Cider support #56206
• [enhanced-parts] Kythe implementation #56207
• [enhanced-parts] Angular compiler implementation #56208
• [enhanced-parts] Intellij implementation #56209
• [enhanced-parts] Language feature docs #56210
• [enhanced-parts] VM service protocol support #56211
• [enhanced-parts] VM debugging support #56212
• [enhanced-parts] Linter Support #59482

[dart-github-bot]

Summary: This issue is a placeholder for a larger feature implementation, "enhanced-parts," which is broken down into multiple sub-issues. The sub-issues cover various aspects of the feature, including its design, implementation, and testing.