ir/basic_block: Forward declare headers where applicable

Now that the constructor and destructors have been placed within the cpp
file, we can forward declare the memory pool data structures. Now, a
change to the memory pool code won't ripple across the entirety of the
IR emitter.

src/frontend/ir/basic_block.cpp

@@ -13,15 +13,17 @@
 #include <fmt/ostream.h>
 
 #include "common/assert.h"
+#include "common/memory_pool.h"
 #include "frontend/A32/types.h"
 #include "frontend/A64/types.h"
 #include "frontend/ir/basic_block.h"
+#include "frontend/ir/cond.h"
 #include "frontend/ir/opcodes.h"
 
 namespace Dynarmic::IR {
 
 Block::Block(const LocationDescriptor& location)
-    : location{location}, end_location{location},
+    : location{location}, end_location{location}, cond{Cond::AL},
       instruction_alloc_pool{std::make_unique<Common::Pool>(sizeof(Inst), 4096)} {}
 
 Block::~Block() = default;

src/frontend/ir/basic_block.h

@@ -13,15 +13,18 @@
 
 #include "common/common_types.h"
 #include "common/intrusive_list.h"
-#include "common/memory_pool.h"
-#include "frontend/ir/cond.h"
 #include "frontend/ir/location_descriptor.h"
 #include "frontend/ir/microinstruction.h"
 #include "frontend/ir/terminal.h"
 #include "frontend/ir/value.h"
 
+namespace Dynarmic::Common {
+class Pool;
+}
+
 namespace Dynarmic::IR {
 
+enum class Cond;
 enum class Opcode;
 
 /**
@@ -142,7 +145,7 @@ private:
     /// Description of the end location of this block
     LocationDescriptor end_location;
     /// Conditional to pass in order to execute this block
-    Cond cond = Cond::AL;
+    Cond cond;
     /// Block to execute next if `cond` did not pass.
     std::optional<LocationDescriptor> cond_failed = {};
     /// Number of cycles this block takes to execute if the conditional fails.