[Fix-it] Support defaulted and variadic arguments in renamed fix-it

[jrose-apple]

• Explanation: Our diagnostics for renamed functions was bailing out whenever any of the arguments were defaulted at the call site, leaving only a fix-it for the base name. If the base name was the same, this was especially confusing.
• Scope: The code path affects all rename diagnostics that include parameters. Correct code should not be affected by this change.
• Issue: SR-2264
• Reviewed by: @jrose-apple (authored by @rintaro)
• Risk: Low.
• Testing: Added to existing compiler regression tests.

---

Before merging this pull request to apple/swift repository:

• Test pull request on Swift continuous integration.

Triggering Swift CI

The swift-ci is triggered by writing a comment on this PR addressed to the GitHub user @swift-ci. Different tests will run depending on the specific comment that you use. The currently available comments are:

Smoke Testing

Platform	Comment
All supported platforms	@swift-ci Please smoke test
All supported platforms	@swift-ci Please smoke test and merge
OS X platform	@swift-ci Please smoke test OS X platform
Linux platform	@swift-ci Please smoke test Linux platform

A smoke test on macOS does the following:

1. Builds the compiler incrementally.
2. Builds the standard library only for macOS. Simulator standard libraries and
   device standard libraries are not built.
3. lldb is not built.
4. The test and validation-test targets are run only for macOS. The optimized
   version of these tests are not run.

A smoke test on Linux does the following:

1. Builds the compiler incrementally.
2. Builds the standard library incrementally.
3. lldb is built incrementally.
4. The swift test and validation-test targets are run. The optimized version of these
   tests are not run.
5. lldb is tested.

Validation Testing

Platform	Comment
All supported platforms	@swift-ci Please test
All supported platforms	@swift-ci Please test and merge
OS X platform	@swift-ci Please test OS X platform
OS X platform	@swift-ci Please benchmark
Linux platform	@swift-ci Please test Linux platform

Lint Testing

Language	Comment
Python	@swift-ci Please Python lint

Note: Only members of the Apple organization can trigger swift-ci.

[jrose-apple]

@swift-ci Please test

[jrose-apple]

Approved by @tkremenek via email.