Organize imports enhancement

[CsCherrYY]

Currently "Organize imports" will do three things:

• Add missing imports
• Remove all unused imports
• Sort existing imports

And there are serveral requests about feature "Organize imports":

Organize import without sorting:

• Better Organize Imports #1575 (comment)
• Better Organize Imports #1575 (comment)

Organize imports (and other code actions) in multiple files:

• Organize Imports action on multiple files #1107
• Organize import at package/folder level #2282
• Support organize imports for multiple files microsoft/vscode-java-pack#1085

We can find rooms to improve. Although we have configuration java.completion.importOrder, it's not such visible and it's hard to "hardcode" a package list for some users. In this way, we can have serveral points to improve:

• Add "Remove all unused imports" quickfix for related warnings Support "remove all unused imports" eclipse-jdtls/eclipse.jdt.ls#2280
  • it just remove all unused imports, will not affect existing valid imports
• Add "Add all missing imports" quickfix for related errors Support "Add all missing imports" eclipse-jdtls/eclipse.jdt.ls#2292
  • it just add all missing imports, will not affect(sort) existing valid imports
• Support "Add all missing import" when pasting Add missing import on paste #2795
  • related API: Add events for copy/paste to allow language extensions to bring using/import statements along microsoft/vscode#30066
• Support code actions (and formatting maybe) in folder level