[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.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>|