Add a lint for toplevel "using namespace" in headers.

We had all sorts of things using the wrong namespaces because everything was
being imported into multiple namespaces if things happened to include certain
headers.  Remove the "using namespace" bits in core headers, fix the resulting
compile issues, add a lint so people stop doing that.

Author: bzbarsky-apple

.github/workflows/lint.yml

@@ -285,3 +285,18 @@ jobs:
               if: always()
               run: |
                   git grep -I -n 'SuccessOrExit([^=)]*(' -- './*' ':(exclude).github/workflows/lint.yml' && exit 1 || exit 0
+
+            # git grep exits with 0 if it finds a match, but we want
+            # to fail (exit nonzero) on match.
+            - name: Check for use of "using namespace" outside of a class/function in headers.
+              if: always()
+              run: |
+                  # Various platforms have `using namespace chip::Ble` in their BLEManager* headers; just exclude those for now.
+                  #
+                  # Exclude platform openiotsdk bits that do this in their persistent storage header.
+                  #
+                  # Also exclude examples (for now) and third_party, which have various instances of this.
+                  #
+                  # Ignore uses of `System::Clock::Literals`, because that's the only way to have things using _ms32 or whatnot
+                  # in a header file.
+                  git grep -I -n -e '^using namespace' --and --not -e 'System::Clock::Literals' -- './**/*.h' ':(exclude)src/platform/*/BLEManager*.h' ':(exclude)src/platform/openiotsdk/KVPsaPsStore.h' ':(exclude)./examples' ':(exclude)./third_party' && exit 1 || exit 0

examples/chip-tool/commands/pairing/IssueNOCChainCommand.h

@@ -46,7 +46,7 @@ class IssueNOCChainCommand : public CHIPCommand
 
     static void OnDeviceNOCChainGeneration(void * context, CHIP_ERROR status, const chip::ByteSpan & noc,
                                            const chip::ByteSpan & icac, const chip::ByteSpan & rcac,
-                                           chip::Optional<chip::IdentityProtectionKeySpan> ipk,
+                                           chip::Optional<chip::Crypto::IdentityProtectionKeySpan> ipk,
                                            chip::Optional<chip::NodeId> adminSubject)
     {
         auto command = static_cast<IssueNOCChainCommand *>(context);