Move ILL data directory setups to class setup

A lot of the ILL tests were using the appendDataSearchSubDir method in
the setup functions. This was resulting in many directories being added
to the config service as the tests ran. They have now been moved to the
setUpClass functions or constructors so they are only added once.

RE #28499

Framework/DataHandling/test/LoadILLDiffractionTest.h

@@ -31,10 +31,12 @@ public:
   }
   static void destroySuite(LoadILLDiffractionTest *suite) { delete suite; }
 
-  void setUp() override {
+  LoadILLDiffractionTest() {
     ConfigService::Instance().appendDataSearchSubDir("ILL/D20/");
     ConfigService::Instance().appendDataSearchSubDir("ILL/D2B/");
+  }
 
+  void setUp() override {
     m_oldFacility = ConfigService::Instance().getFacility().name();
     ConfigService::Instance().setFacility("ILL");
 

Framework/DataHandling/test/LoadILLSANSTest.h

@@ -37,7 +37,13 @@ public:
   static LoadILLSANSTest *createSuite() { return new LoadILLSANSTest(); }
   static void destroySuite(LoadILLSANSTest *suite) { delete suite; }
 
-  void setUp() override { ConfigService::Instance().setFacility("ILL"); }
+  LoadILLSANSTest() {
+    ConfigService::Instance().appendDataSearchSubDir("ILL/D11/");
+    ConfigService::Instance().appendDataSearchSubDir("ILL/D22/");
+    ConfigService::Instance().appendDataSearchSubDir("ILL/D33/");
+    ConfigService::Instance().appendDataSearchSubDir("ILL/D16/");
+    ConfigService::Instance().setFacility("ILL");
+  }
 
   void tearDown() override { AnalysisDataService::Instance().clear(); }
 

Framework/PythonInterface/test/python/plugins/algorithms/LoadAndMergeTest.py

@@ -11,11 +11,14 @@ from mantid.simpleapi import LoadAndMerge, config, mtd
 
 class LoadAndMergeTest(unittest.TestCase):
 
+    @classmethod
+    def setUpClass(cls):
+        config.appendDataSearchSubDir('ILL/IN16B/')
+        config.appendDataSearchSubDir('ILL/D20/')
+
     def setUp(self):
         config['default.facility'] = 'ILL'
         config['default.instrument'] = 'IN16B'
-        config.appendDataSearchSubDir('ILL/IN16B/')
-        config.appendDataSearchSubDir('ILL/D20/')
 
     def test_single_run_load(self):
         out1 = LoadAndMerge(Filename='170257')

Framework/PythonInterface/test/python/plugins/algorithms/LoadLampTest.py

@@ -10,7 +10,8 @@ import unittest
 
 class LoadLampTest(unittest.TestCase):
 
-    def setUp(self):
+    @classmethod
+    def setUpClass(cls):
         config.appendDataSearchSubDir('ILL/LAMP/')
 
     def tearDown(self):

Framework/PythonInterface/test/python/plugins/algorithms/WorkflowAlgorithms/PowderILLDetectorScanTest.py

@@ -13,10 +13,13 @@ from mantid.simpleapi import PowderILLDetectorScan, config, mtd
 # More options are covered by system tests, since it takes too long for a unit test.
 class PowderILLDetectorScanTest(unittest.TestCase):
 
+    @classmethod
+    def setUpClass(cls):
+        config.appendDataSearchSubDir('ILL/D2B/')
+
     def setUp(self):
         config['default.facility'] = 'ILL'
         config['default.instrument'] = 'D2B'
-        config.appendDataSearchSubDir('ILL/D2B/')
 
     def tearDown(self):
         mtd.clear()

Framework/PythonInterface/test/python/plugins/algorithms/WorkflowAlgorithms/PowderILLParameterScanTest.py

@@ -13,10 +13,13 @@ class PowderILLParameterScanTest(unittest.TestCase):
 
     _runs = '967087:967088'
 
+    @classmethod
+    def setUpClass(cls):
+        config.appendDataSearchSubDir('ILL/D20/')
+
     def setUp(self):
         config['default.facility'] = 'ILL'
         config['default.instrument'] = 'D20'
-        config.appendDataSearchSubDir('ILL/D20/')
 
     def tearDown(self):
         mtd.remove('red')

Framework/PythonInterface/test/python/plugins/algorithms/WorkflowAlgorithms/SANSILLReductionTest.py

@@ -15,10 +15,12 @@ class SANSILLReductionTest(unittest.TestCase):
     _facility = None
     _instrument = None
 
-    def setUp(self):
+    @classmethod
+    def setUpClass(cls):
         config.appendDataSearchSubDir('ILL/D11/')
         config.appendDataSearchSubDir('ILL/D33/')
 
+    def setUp(self):
         self._facility = config['default.facility']
         self._instrument = config['default.instrument']