[LL] add tests for FirDeclarationForCompiledElementSearcher

build stub if was not able to load:
expected that in IDE stubs would always be found in the index, for tests -
build from virtual file

analysis/low-level-api-fir/testdata/getOrBuildFirForStdLib/emptyArray.kt

@@ -0,0 +1,8 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+// WITH_STDLIB
+
+val d = empty<caret>Array<String>()

analysis/low-level-api-fir/testdata/getOrBuildFirForStdLib/emptyArray.txt

@@ -0,0 +1,6 @@
+KT element: KtNamedFunction
+FIR element: FirSimpleFunctionImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+public final inline [ResolvedTo(BODY_RESOLVE)] fun <@R|kotlin/internal/PureReifiable|() reified [ResolvedTo(BODY_RESOLVE)] T> emptyArray(): R|kotlin/Array<T>|

analysis/low-level-api-fir/testdata/getOrBuildFirForStdLib/flattenArray.kt

@@ -0,0 +1,8 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+// WITH_STDLIB
+
+val d = arrayOf(arrayOf("1", "2")).fla<caret>tten()

analysis/low-level-api-fir/testdata/getOrBuildFirForStdLib/flattenArray.txt

@@ -0,0 +1,6 @@
+KT element: KtNamedFunction
+FIR element: FirSimpleFunctionImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+public final [ResolvedTo(BODY_RESOLVE)] fun <[ResolvedTo(BODY_RESOLVE)] T> R|kotlin/Array<out kotlin/Array<out T>>|.flatten(): R|kotlin/collections/List<T>|

analysis/low-level-api-fir/testdata/getOrBuildFirForStdLib/fromBits.kt

@@ -0,0 +1,8 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+// WITH_STDLIB
+
+val d = Double.from<caret>Bits(0x400921fb54442d18L)

analysis/low-level-api-fir/testdata/getOrBuildFirForStdLib/fromBits.txt

@@ -0,0 +1,6 @@
+KT element: KtNamedFunction
+FIR element: FirSimpleFunctionImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+@R|kotlin/SinceKotlin|(version = String(1.2)) @R|kotlin/internal/InlineOnly|() public final inline [ResolvedTo(BODY_RESOLVE)] fun @RECEIVER:R|kotlin/SinceKotlin|(version = String(1.2)) @RECEIVER:R|kotlin/internal/InlineOnly|() R|kotlin/Double.Companion|.fromBits([ResolvedTo(BODY_RESOLVE)] bits: R|kotlin/Long|): R|kotlin/Double|