build/meson: rename platform tests to use same name as autotools

First of all, all file names in our source-tree should be unique. We should
not have stuff like "libnm-core/tests/test-general.c" and "src/tests/test-general.c".
The problem here are the C source files, and consequently also the test
binaries have duplicate names. We should avoid that in general. However,
our binaries should have a matching name with the C source. If
"test-general.c" is not good enough, that needs renaming. Not building
"platform-test-general" out of it.

On the other hand, all our tests should have a filename "*/tests/test-*", like
they do for autotools.

Rename the meson platform tests.

It's also important because "tools/run-nm-test.sh" relies on the test
name to workaround valgrind warnings.

src/devices/tests/meson.build

@@ -9,7 +9,6 @@ foreach test_unit: test_units
     test_unit + '.c',
     dependencies: test_nm_dep,
   )
-
   test(
     'devices/' + test_unit,
     test_script,

src/platform/tests/meson.build

@@ -13,11 +13,10 @@ test_units = [
 
 foreach test_unit: test_units
   exe = executable(
-    'platform-' + test_unit[0],
+    test_unit[0],
     test_unit[1],
     dependencies: test_unit[2],
   )
-
   test(
     'platform/' + test_unit[0],
     test_script,
@@ -26,10 +25,8 @@ foreach test_unit: test_units
   )
 endforeach
 
-test = 'monitor'
-
 executable(
-  test,
-  test + '.c',
+  'monitor',
+  'monitor.c',
   dependencies: test_nm_dep,
 )