Add flag to allow using kotlin.Result as a return type

#KT-26659 Fixed

compiler/testData/cli/js/jsExtraHelp.out

@@ -4,6 +4,7 @@ where advanced options include:
   -Xfriend-modules-disabled  Disable internal declaration export
   -Xtyped-arrays             Translate primitive arrays to JS typed arrays
   -Xallow-kotlin-package     Allow compiling code in package 'kotlin' and allow not requiring kotlin.stdlib in module-info
+  -Xallow-result-return-type Allow compiling code when `kotlin.Result` is used as a return type
   -Xcommon-sources=<path>    Sources of the common module that need to be compiled together with this module in the multi-platform mode.
                              Should be a subset of sources passed as free arguments
   -Xcoroutines={enable|warn|error}

compiler/testData/cli/jvm/extraHelp.out

@@ -62,6 +62,7 @@ where advanced options include:
   -Xuse-old-class-files-reading Use old class files reading implementation (may slow down the build and should be used in case of problems with the new implementation)
   -Xuse-type-table           Use type table in metadata serialization
   -Xallow-kotlin-package     Allow compiling code in package 'kotlin' and allow not requiring kotlin.stdlib in module-info
+  -Xallow-result-return-type Allow compiling code when `kotlin.Result` is used as a return type
   -Xcommon-sources=<path>    Sources of the common module that need to be compiled together with this module in the multi-platform mode.
                              Should be a subset of sources passed as free arguments
   -Xcoroutines={enable|warn|error}

compiler/testData/cli/jvm/flagAllowingResultAsReturnType.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/flagAllowingResultAsReturnType.kt
+-Xallow-result-return-type
+-d
+$TEMP_DIR$

compiler/testData/cli/jvm/flagAllowingResultAsReturnType.kt

@@ -0,0 +1 @@
+fun foo(): Result<Int> = TODO()

compiler/testData/cli/jvm/flagAllowingResultAsReturnType.out

@@ -0,0 +1 @@
+OK