[analysis_server] Handle Color.withXxx() methods for Flutter colors in LSP

Before this change, `Color.foo.withValues(red:100)` would show a misleading preview/picker for `Color.foo` ignoring the call to `withValues()`. With this, we handle all of the built-in (non-deprecated) `withXxx()` methods.

Fixes https://github.com/Dart-Code/Dart-Code/issues/6143

Change-Id: I5f4be30a85d124d226fe98a93ab9a4ea2e3da310
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/542060
Reviewed-by: Keerti Parthasarathy <keertip@google.com>
Commit-Queue: Keerti Parthasarathy <keertip@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>