Cleanup wget browser tests. NFC (#23907)

Rename `emscripten_fs_api_browser.c` to `test_emscripten_async_wget.c`
since that seems to be the primary thing its testing.

Remove `emscripten_fs_api_browser2.c` since that just seems like a
strict subset of what is tested already in `emscripten_fs_api_browser.c`

Rename `test_emscripten_async_wget_side_module` source files.

Group all wget tests together in `test_browser.py`.

Author: sbc100

test/emscripten_fs_api_browser2.c

@@ -1892,15 +1892,6 @@ def setup():
   def test_emscripten_api_infloop(self):
     self.btest_exit('emscripten_api_browser_infloop.cpp')
 
-  @also_with_wasmfs
-  def test_emscripten_fs_api(self):
-    shutil.copy(test_file('screenshot.png'), '.') # preloaded *after* run
-    self.btest_exit('emscripten_fs_api_browser.c', emcc_args=['-lSDL'])
-
-  def test_emscripten_fs_api2(self):
-    self.btest_exit('emscripten_fs_api_browser2.c', emcc_args=['-sASSERTIONS=0'])
-    self.btest_exit('emscripten_fs_api_browser2.c', emcc_args=['-sASSERTIONS=1'])
-
   @parameterized({
     '': ([],),
     'pthreads': (['-pthread', '-sPROXY_TO_PTHREAD', '-sEXIT_RUNTIME'],),
@@ -2516,6 +2507,24 @@ def test_worker_api_with_pthread_compilation_fails(self):
     stderr = self.expect_fail([EMCC, 'hello.o', '-o', 'a.js', '-g', '--closure=1', '-pthread', '-sBUILD_AS_WORKER'])
     self.assertContained("pthreads + BUILD_AS_WORKER require separate modes that don't work together, see https://github.com/emscripten-core/emscripten/issues/8854", stderr)
 
+  @also_with_wasmfs
+  def test_wget(self):
+    create_file('test.txt', 'emscripten')
+    self.btest_exit('test_wget.c', emcc_args=['-sASYNCIFY'])
+
+  def test_wget_data(self):
+    create_file('test.txt', 'emscripten')
+    self.btest_exit('test_wget_data.c', emcc_args=['-O2', '-g2', '-sASYNCIFY'])
+
+  @also_with_wasmfs
+  @parameterized({
+    '': ([],),
+    'O2': (['-O2'],),
+  })
+  def test_emscripten_async_wget(self, args):
+    shutil.copy(test_file('screenshot.png'), '.') # preloaded *after* run
+    self.btest_exit('test_emscripten_async_wget.c', emcc_args=['-lSDL'] + args)
+
   @also_with_wasmfs
   def test_emscripten_async_wget2(self):
     self.btest_exit('test_emscripten_async_wget2.cpp')
@@ -2526,8 +2535,8 @@ def test_emscripten_async_wget2_data(self):
     self.btest('test_emscripten_async_wget2_data.cpp', expected='0')
 
   def test_emscripten_async_wget_side_module(self):
-    self.emcc(test_file('browser_module.c'), ['-o', 'lib.wasm', '-O2', '-sSIDE_MODULE'])
-    self.btest_exit('browser_main.c', emcc_args=['-O2', '-sMAIN_MODULE=2'])
+    self.emcc(test_file('test_emscripten_async_wget_side_module.c'), ['-o', 'lib.wasm', '-O2', '-sSIDE_MODULE'])
+    self.btest_exit('test_emscripten_async_wget_main_module.c', emcc_args=['-O2', '-sMAIN_MODULE=2'])
 
   @parameterized({
     '': ([],),
@@ -2845,15 +2854,6 @@ def test_html5_mouse(self, opts):
   def test_sdl_mousewheel(self, opts):
     self.btest_exit('test_sdl_mousewheel.c', emcc_args=opts + ['-DAUTOMATE_SUCCESS=1', '-lSDL', '-lGL'])
 
-  @also_with_wasmfs
-  def test_wget(self):
-    create_file('test.txt', 'emscripten')
-    self.btest_exit('test_wget.c', emcc_args=['-sASYNCIFY'])
-
-  def test_wget_data(self):
-    create_file('test.txt', 'emscripten')
-    self.btest_exit('test_wget_data.c', emcc_args=['-O2', '-g2', '-sASYNCIFY'])
-
   @also_with_wasm2js
   @parameterized({
     '': ([],),