[Tests] Run KMP tests in Analysis API LL FIR test suites

New tests are red in current commit!
All `.ll.kt` files are just copies of `.fir.kt` or `.kt`. This will be
fixed in the next commit to clearly show difference between LL and FIR.

The original purpose of this change was to test
`ACTUAL_ANNOTATIONS_NOT_MATCH_EXPECT` diagnostic, for which FIR checker
will be run only in IDE (to be changed in next MR), so its reports
a lost from usual KMP tests.
But this looks like a useful change for all KMP tests, not only this
diagnostic.

^KT-62559

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/AbstractCompilerBasedTestForFir.kt

@@ -59,7 +59,13 @@ abstract class AbstractCompilerBasedTestForFir : AbstractCompilerBasedTest() {
 
         useMetaTestConfigurators(::LLFirMetaTestConfigurator)
         useAfterAnalysisCheckers(::LLFirIdenticalChecker)
-        useAfterAnalysisCheckers(::LLFirDivergenceCommentChecker)
+
+        // For multiplatform tests it's expected that LL and FIR diverge,
+        // because IR actualizer doesn't run in IDE mode tests.
+        forTestsNotMatching("compiler/testData/diagnostics/tests/multiplatform/*") {
+            useAfterAnalysisCheckers(::LLFirDivergenceCommentChecker)
+        }
+
         useAfterAnalysisCheckers(::LLFirTestSuppressor)
     }
 

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/LLFirDivergenceUtils.kt

@@ -21,7 +21,7 @@ fun String.removeLlFirDivergenceDirective(trimLines: Boolean): String {
     return if (findDirectiveInLines(iterator)) {
         // `trimStart` ensures that the `LL_FIR_DIVERGENCE` directive can be separated from the rest of the file by blank lines.
         iterator.asSequence().concatLines(trimLines).trimStart()
-    } else this
+    } else this.trim() // Trim start and end newlines in file if directive not found
 }
 
 private fun Sequence<String>.concatLines(trimLines: Boolean): String =