Allow to embed source files into JS source maps

compiler/testData/cli/js/jsHelp.out

@@ -7,6 +7,8 @@ where possible options include:
   -source-map-prefix         Prefix for paths in a source map
   -source-map-source-roots <path>
                              Base directories which are used to calculate relative paths to source files in source map
+  -source-map-embed-sources { always, never, inlining }
+                             Embed source files into source map
   -meta-info                 Generate .meta.js and .kjsm files with metadata. Use to create a library
   -target { v5 }             Generate JS files for specific ECMA version
   -module-kind { plain, amd, commonjs, umd }

compiler/testData/cli/js/sourceMapEmbedSources.args

@@ -0,0 +1,7 @@
+$TESTDATA_DIR$/sourceMap.kt
+-no-stdlib
+-source-map
+-source-map-embed-sources
+always
+-output
+$TEMP_DIR$/out.js

compiler/testData/cli/js/sourceMapEmbedSources.out

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

compiler/testData/cli/js/sourceMapEmbedSources.test

@@ -0,0 +1,3 @@
+// EXISTS: out.js
+// CONTAINS: out.js.map, "sourceMap.kt"
+// CONTAINS: out.js.map, "var log = \"\"\n\nfun foo(x: String) {