fix(telemetry): keep the telemetry-off build clean

A -DXRPL_ENABLE_TELEMETRY=0 build expands every XRPL_METRIC_* macro to
nothing, so anything whose only use sits inside one looks unused.

- MetricsRegistry::hasPipeline touches no member in that build, so
  clang-tidy asks for it to be static. Making it static would give the two
  builds different signatures, so suppress it the way Recording.h already
  does for the same reason.
- PathRequest.cpp's only use of MetricMacros.h is such a macro, so mark the
  include as kept.
- AppMetricGauges.cpp names MetricsRegistry and beast::Journal in a
  constructor signature that is compiled either way, so their includes move
  outside the telemetry guard.

src/libxrpl/telemetry/MetricsRegistry.cpp

@@ -404,6 +404,10 @@ MetricsRegistry::stop()
 #endif  // XRPL_ENABLE_TELEMETRY
 }
 
+// This reads provider_ when telemetry is compiled in and touches no member
+// when it is not, so clang-tidy asks for it to be static. Making it static
+// would give the two builds different signatures.
+// NOLINTBEGIN(readability-convert-member-functions-to-static)
 bool
 MetricsRegistry::hasPipeline() const noexcept
 {
@@ -413,6 +417,7 @@ MetricsRegistry::hasPipeline() const noexcept
     return false;
 #endif
 }
+// NOLINTEND(readability-convert-member-functions-to-static)
 
 // -----------------------------------------------------------------
 // Synchronous instrument recording — RPC metrics

src/xrpld/rpc/detail/PathRequest.cpp

@@ -39,7 +39,7 @@
 #include <xrpl/resource/Consumer.h>
 #include <xrpl/server/InfoSub.h>
 #include <xrpl/server/LoadFeeTrack.h>
-#include <xrpl/telemetry/MetricMacros.h>
+#include <xrpl/telemetry/MetricMacros.h>  // IWYU pragma: keep
 #include <xrpl/telemetry/Redaction.h>
 #include <xrpl/telemetry/SpanGuard.h>
 #include <xrpl/tx/paths/RippleCalc.h>

src/xrpld/telemetry/AppMetricGauges.cpp

@@ -24,6 +24,11 @@
 
 #include <xrpld/telemetry/AppMetricGauges.h>
 
+// Both name types in the constructor signature, which is compiled in either
+// way, so they belong outside the telemetry guard below.
+#include <xrpl/beast/utility/Journal.h>
+#include <xrpl/telemetry/MetricsRegistry.h>
+
 #ifdef XRPL_ENABLE_TELEMETRY
 
 // The app and overlay includes below are why
@@ -56,7 +61,6 @@
 #include <xrpl/basics/CountedObject.h>
 #include <xrpl/basics/Log.h>
 #include <xrpl/basics/UptimeClock.h>
-#include <xrpl/beast/utility/Journal.h>
 #include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/json/json_value.h>
 #include <xrpl/nodestore/Database.h>