Build: implement useBootstrapStdlib flag

Excludes stdlib projects from build and uses bootstrap stdlib artifacts

 #KT-29205

libraries/kotlinx-metadata/build.gradle.kts

@@ -14,7 +14,7 @@ sourceSets {
 }
 
 dependencies {
-    compile(project(":kotlin-stdlib"))
+    compile(kotlinStdlib())
     compileOnly(project(":core:metadata"))
     compileOnly(protobufLite())
 }

libraries/kotlinx-metadata/jvm/build.gradle.kts

@@ -36,7 +36,7 @@ configurations.getByName("compileOnly").extendsFrom(shadows)
 configurations.getByName("testCompile").extendsFrom(shadows)
 
 dependencies {
-    compile(project(":kotlin-stdlib"))
+    compile(kotlinStdlib())
     shadows(project(":kotlinx-metadata"))
     shadows(project(":core:metadata"))
     shadows(project(":core:metadata.jvm"))