scripts: twister: minor speedup in apply_filters

Move a check to run earlier in a for-loop to minimize doing unnecessary
work like creating TestInstance class instances.

This is a very minor optimization when the number of testsuites are low.
But starts to count when there are a lot of testsuites.

Signed-off-by: Guðni Már Gilbert <gudni.m.g@gmail.com>

Author: gudnimg

scripts/pylib/twister/twisterlib/testplan.py

@@ -889,6 +889,10 @@ def apply_filters(self, **kwargs):
             for itoolchain, plat in itertools.product(
                 ts.integration_toolchains or [None], platform_scope
             ):
+                if (plat.arch == "unit") != (ts.type == "unit"):
+                    # Discard silently
+                    continue
+
                 if itoolchain:
                     toolchain = itoolchain
                 elif plat.arch in ['posix', 'unit']:
@@ -909,10 +913,6 @@ def apply_filters(self, **kwargs):
                 if not force_platform and self.check_platform(plat,exclude_platform):
                     instance.add_filter("Platform is excluded on command line.", Filters.CMD_LINE)
 
-                if (plat.arch == "unit") != (ts.type == "unit"):
-                    # Discard silently
-                    continue
-
                 if ts.modules and self.modules and not set(ts.modules).issubset(set(self.modules)):
                     instance.add_filter(
                         f"one or more required modules not available: {','.join(ts.modules)}",