Minor: get line start without whitespaces in KotlinExtraVariablesProvider

#KT-10183 Fxied

idea/testData/debugger/tinyApp/outs/evFunctionDeclaration.out

@@ -0,0 +1,24 @@
+LineBreakpoint created at evFunctionDeclaration.kt:5
+!JDK_HOME!\bin\java -agentlib:jdwp=transport=dt_socket,address=!HOST_NAME!:!HOST_PORT!,suspend=y,server=n -Dfile.encoding=!FILE_ENCODING! -classpath !OUTPUT_PATH!;!KOTLIN_RUNTIME!;!CUSTOM_LIBRARY!;!RT_JAR! evFunctionDeclaration.EvFunctionDeclarationKt
+Connected to the target VM, address: '!HOST_NAME!:PORT_NAME!', transport: 'socket'
+evFunctionDeclaration.kt:5
+package evFunctionDeclaration
+
+class A(val a: Int) {
+    //Breakpoint!
+    fun foo() = a
+}
+
+fun main(args: Array<String>) {
+    A(1).foo()
+}
+
+// PRINT_FRAME
+Compile bytecode for a
+ frame    = foo():5, A {evFunctionDeclaration}
+   this     = this = {evFunctionDeclaration.A@uniqueID}
+     field    = a: int = 1 (sp = evFunctionDeclaration.kt, 3)
+   extra    = a
+Disconnected from the target VM, address: '!HOST_NAME!:PORT_NAME!', transport: 'socket'
+
+Process finished with exit code 0