init: replace Result<> with expected<>

Android-base has an implementation of the future std::expected<>.
This provides the same baseline functionality as Result<>, so use it
instead of our own version.

Bug: 132145659
Test: boot, init unit tests
Change-Id: I11e61bcb5719b262a6420483ed51a762826a9e23
diff --git a/init/keychords.cpp b/init/keychords.cpp
index f5ac44f..d0ca3e7 100644
--- a/init/keychords.cpp
+++ b/init/keychords.cpp
@@ -41,7 +41,7 @@
 
 Keychords::~Keychords() noexcept {
     if (inotify_fd_ >= 0) {
-        epoll_->UnregisterHandler(inotify_fd_).IgnoreError();
+        epoll_->UnregisterHandler(inotify_fd_);
         ::close(inotify_fd_);
     }
     while (!registration_.empty()) GeteventCloseDevice(registration_.begin()->first);
@@ -212,7 +212,7 @@
     auto it = registration_.find(device);
     if (it == registration_.end()) return;
     auto fd = (*it).second;
-    epoll_->UnregisterHandler(fd).IgnoreError();
+    epoll_->UnregisterHandler(fd);
     registration_.erase(it);
     ::close(fd);
 }