Fix ParticleContainer: amrex::Long pid

```
error: narrowing conversion from 'amrex::Long' (aka 'long') to signed type 'int' is implementation-defined [bugprone-narrowing-conversions,-warnings-as-errors]
```

Author: ax3l

Source/Particles/PhysicalParticleContainer.cpp

@@ -1080,10 +1080,10 @@ PhysicalParticleContainer::AddPlasma (PlasmaInjector const& plasma_injector, int
 
         // Max number of new particles. All of them are created,
         // and invalid ones are then discarded
-        const int max_new_particles = Scan::ExclusiveSum(counts.size(), counts.data(), offset.data());
+        const amrex::Long max_new_particles = Scan::ExclusiveSum(counts.size(), counts.data(), offset.data());
 
         // Update NextID to include particles created in this function
-        int pid;
+        amrex::Long pid;
 #ifdef AMREX_USE_OMP
 #pragma omp critical (add_plasma_nextid)
 #endif
@@ -1092,7 +1092,7 @@ PhysicalParticleContainer::AddPlasma (PlasmaInjector const& plasma_injector, int
             ParticleType::NextID(pid+max_new_particles);
         }
         WARPX_ALWAYS_ASSERT_WITH_MESSAGE(
-            static_cast<amrex::Long>(pid) + static_cast<amrex::Long>(max_new_particles) < LongParticleIds::LastParticleID,
+            pid + max_new_particles < LongParticleIds::LastParticleID,
             "ERROR: overflow on particle id numbers");
 
         const int cpuid = ParallelDescriptor::MyProc();
@@ -1103,8 +1103,8 @@ PhysicalParticleContainer::AddPlasma (PlasmaInjector const& plasma_injector, int
             DefineAndReturnParticleTile(lev, grid_id, tile_id);
         }
 
-        auto old_size = particle_tile.size();
-        auto new_size = old_size + max_new_particles;
+        amrex::Long old_size = particle_tile.size();
+        amrex::Long new_size = old_size + max_new_particles;
         particle_tile.resize(new_size);
 
         auto& soa = particle_tile.GetStructOfArrays();
@@ -1639,10 +1639,10 @@ PhysicalParticleContainer::AddPlasmaFlux (PlasmaInjector const& plasma_injector,
 
         // Max number of new particles. All of them are created,
         // and invalid ones are then discarded
-        const int max_new_particles = Scan::ExclusiveSum(counts.size(), counts.data(), offset.data());
+        const amrex::Long max_new_particles = Scan::ExclusiveSum(counts.size(), counts.data(), offset.data());
 
         // Update NextID to include particles created in this function
-        int pid;
+        amrex::Long pid;
 #ifdef AMREX_USE_OMP
 #pragma omp critical (add_plasma_nextid)
 #endif
@@ -1651,15 +1651,15 @@ PhysicalParticleContainer::AddPlasmaFlux (PlasmaInjector const& plasma_injector,
             ParticleType::NextID(pid+max_new_particles);
         }
         WARPX_ALWAYS_ASSERT_WITH_MESSAGE(
-            static_cast<amrex::Long>(pid) + static_cast<amrex::Long>(max_new_particles) < LongParticleIds::LastParticleID,
+            pid + max_new_particles < LongParticleIds::LastParticleID,
             "overflow on particle id numbers");
 
         const int cpuid = ParallelDescriptor::MyProc();
 
         auto& particle_tile = tmp_pc.DefineAndReturnParticleTile(0, grid_id, tile_id);
 
-        auto old_size = particle_tile.size();
-        auto new_size = old_size + max_new_particles;
+        amrex::Long old_size = particle_tile.size();
+        amrex::Long new_size = old_size + max_new_particles;
         particle_tile.resize(new_size);
 
         auto& soa = particle_tile.GetStructOfArrays();