Writer fixes (#1469)

* Fixes for RustWriter bugs #1465 & #1459

* Fix behavior causing extra newlines in docs

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/rustlang/RustWriter.kt

@@ -253,16 +253,16 @@ fun RustWriter.containerDocs(text: String, vararg args: Any): RustWriter {
  *    - Empty newlines are removed
  */
 fun <T : AbstractCodeWriter<T>> T.docs(text: String, vararg args: Any, newlinePrefix: String = "/// "): T {
+    // Because writing docs relies on the newline prefix, ensure that there was a new line written
+    // before we write the docs
+    this.ensureNewline()
     pushState()
     setNewlinePrefix(newlinePrefix)
     val cleaned = text.lines()
         .joinToString("\n") {
             // Rustdoc warns on tabs in documentation
             it.trimStart().replace("\t", "  ")
         }
-    // Because writing docs relies on the newline prefix, ensure that there was a new line written
-    // before we write the docs
-    this.ensureNewline()
     write(cleaned, *args)
     popState()
     return this

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/generators/client/FluentClientDecorator.kt

@@ -448,7 +448,7 @@ class FluentClientGenerator(
                 Fluent builders are created through the [`Client`](crate::client::Client) by calling
                 one if its operation methods. After parameters are set using the builder methods,
                 the `send` method can be called to initiate the request.
-                """,
+                """.trim(),
                 newlinePrefix = "//! "
             )
             operations.forEach { operation ->