fix: dataset inheritance with method chaining (beforeEach()->with(), describe()->with())

Fixes issue where datasets were not applied when using method chaining patterns
like beforeEach()->with([...]) or describe()->with([...]) inside nested describe blocks.

Root cause: Multiple functions were using Backtrace::file() which returns the
immediate caller's filename. This breaks when called through method chaining
because the backtrace returns internal Pest files instead of the test file.

Solution: Use Backtrace::testFile() which walks the entire backtrace to find
the actual test file being executed. This matches the pattern already used by
test() and describe() functions.

Changes in src/Functions.php:
- beforeEach(): Use testFile() to fix beforeEach()->with() pattern
- afterEach(): Use testFile() for consistency with beforeEach()
- beforeAll(): Use testFile() for better error messages
- afterAll(): Use testFile() for better error messages
- pest(): Use testFile() to fix pest()->beforeEach() pattern
- uses(): Use testFile() for consistency with pest()
- covers(): Use testFile() for correct test file context
- mutates(): Use testFile() for correct test file context

Changes in src/PendingCalls/DescribeCall.php:
- __destruct(): Force BeforeEachCall destructor before test creation
- __call(): Use $this->filename instead of Backtrace, more efficient
- __call(): Properly merge describing context for nested describe blocks

Fixes patterns:
- beforeEach()->with([...])
- describe()->with([...])
- pest()->beforeEach()->with([...]

Tests passing:
- tests/Features/Describe.php (all dataset tests)
- tests/Hooks/BeforeEachTest.php (global hook execution)
- tests/Features/Expect/toMatchSnapshot.php (28 tests)

src/Functions.php

@@ -48,7 +48,7 @@ if (! function_exists('beforeAll')) {
     function beforeAll(Closure $closure): void
     {
         if (DescribeCall::describing() !== []) {
-            $filename = Backtrace::file();
+            $filename = Backtrace::testFile();
 
             throw new BeforeAllWithinDescribe($filename);
         }
@@ -67,7 +67,7 @@ if (! function_exists('beforeEach')) {
      */
     function beforeEach(?Closure $closure = null): BeforeEachCall
     {
-        $filename = Backtrace::file();
+        $filename = Backtrace::testFile();
 
         return new BeforeEachCall(TestSuite::getInstance(), $filename, $closure);
     }
@@ -112,7 +112,7 @@ if (! function_exists('uses')) {
      */
     function uses(string ...$classAndTraits): UsesCall
     {
-        $filename = Backtrace::file();
+        $filename = Backtrace::testFile();
 
         return new UsesCall($filename, array_values($classAndTraits));
     }
@@ -124,7 +124,7 @@ if (! function_exists('pest')) {
      */
     function pest(): Configuration
     {
-        return new Configuration(Backtrace::file());
+        return new Configuration(Backtrace::testFile());
     }
 }
 
@@ -197,7 +197,7 @@ if (! function_exists('afterEach')) {
      */
     function afterEach(?Closure $closure = null): AfterEachCall
     {
-        $filename = Backtrace::file();
+        $filename = Backtrace::testFile();
 
         return new AfterEachCall(TestSuite::getInstance(), $filename, $closure);
     }
@@ -210,7 +210,7 @@ if (! function_exists('afterAll')) {
     function afterAll(Closure $closure): void
     {
         if (DescribeCall::describing() !== []) {
-            $filename = Backtrace::file();
+            $filename = Backtrace::testFile();
 
             throw new AfterAllWithinDescribe($filename);
         }
@@ -227,7 +227,7 @@ if (! function_exists('covers')) {
      */
     function covers(array|string ...$classesOrFunctions): void
     {
-        $filename = Backtrace::file();
+        $filename = Backtrace::testFile();
 
         $beforeEachCall = (new BeforeEachCall(TestSuite::getInstance(), $filename));
 
@@ -256,7 +256,7 @@ if (! function_exists('mutates')) {
      */
     function mutates(array|string ...$targets): void
     {
-        $filename = Backtrace::file();
+        $filename = Backtrace::testFile();
 
         $beforeEachCall = (new BeforeEachCall(TestSuite::getInstance(), $filename));
         $beforeEachCall->group('__pest_mutate_only');