[LL FIR] FileStructure: resolve FirFile to body phase as all other elements

This is the correct behavior as we have to resolve to body phase
to build CFG and run diagnostics collector correctly

^KT-65780 Fixed

analysis/low-level-api-fir/testData/getOrBuildFir/inImport/firstImportNamePartScript.txt

@@ -6,7 +6,7 @@ FIR element rendered:
 import a.b.c
 
 FIR FILE:
-FILE: [ResolvedTo(IMPORTS)] firstImportNamePartScript.kts
+FILE: [ResolvedTo(BODY_RESOLVE)] firstImportNamePartScript.kts
     context(<script>@kotlin.script.templates.standard.ScriptTemplateWithArgs)
     SCRIPT: [ResolvedTo(RAW_FIR)] <script-firstImportNamePartScript.kts>
         [ResolvedTo(RAW_FIR)] lval args: R|kotlin/Array<kotlin/String>|