to simplify testing

completion: don't Tab-overwrite in read-only part of injected file (EA-116414 - assert: DocumentWindowImpl.deleteString)

Follow-up to bbebd174

Inlining action: show conflicts when replacing variable with variable that might change (IDEA-204546)

Inlining action: show conflict if replacement variable changes before last read of original variable (IDEA-204546)

Later implementation method will be modified to do save in pooled thread anyway.

SaveResult introduced because coroutines can executes on different threads — so, lock free approach is used (coroutine returns own result and it's appended to total result (synchronously, for simplicity, because it is enough and no need to complicate))