pw_kvs: Minor adjustments for -Weffc++

Make a few minor updates to pw_kvs to silence -Weffc++ warnings. Pigweed
does not support -Weffc++ in general, since it enforces compliance with
a style guide it does not follow.

Fixes: b/234874590, b/234875054
Change-Id: I97a85ea175b5deb900de07c3095daee2116e2666
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/101301
Reviewed-by: Armando Montanez <amontanez@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>

pw_kvs/public/pw_kvs/alignment.h

@@ -57,6 +57,9 @@ class AlignedWriter {
     // TODO(hepler): Add DCHECK to ensure that buffer.size() >= alignment_bytes.
   }
 
+  AlignedWriter(const AlignedWriter&) = delete;
+  AlignedWriter& operator=(const AlignedWriter&) = delete;
+
   ~AlignedWriter() {
     Flush().IgnoreError();  // TODO(pwbug/387): Handle Status properly
   }

pw_kvs/public/pw_kvs/key_value_store.h

@@ -610,7 +610,10 @@ class KeyValueStoreBuffer : public KeyValueStore {
                       sectors_,
                       temp_sectors_to_skip_,
                       key_descriptors_,
-                      addresses_) {
+                      addresses_),
+        sectors_(),
+        key_descriptors_(),
+        formats_() {
     std::copy(formats.begin(), formats.end(), formats_.begin());
   }