Fix crash on bazel mod error containing %

`bazel mod show_extension @foo//:extensions.bzl%go_sdk`resulted in the crash:
```
java.util.IllegalFormatConversionException: g != java.lang.String
```

Also makes an error more readable by swapping a `:`.

Closes #20627.

PiperOrigin-RevId: 592942775
Change-Id: Ida5c234413c1647f81d3702bb9deeedcdd93df12

src/main/java/com/google/devtools/build/lib/bazel/commands/ModCommand.java

@@ -278,7 +278,7 @@ private BlazeCommandResult execInternal(CommandEnvironment env, OptionsParsingRe
  baseModule.getUnusedDeps()));
  } catch (InvalidArgumentException | OptionsParsingException e) {
  throw new InvalidArgumentException(
- String.format("In extension argument: %s %s", arg, e.getMessage()),
+ String.format("In extension argument %s: %s", arg, e.getMessage()),
  Code.INVALID_ARGUMENTS,
  e);
  }
@@ -494,13 +494,10 @@ private static ImmutableSortedSet<ModuleExtensionId> extensionArgListToIds(
 
  private static BlazeCommandResult reportAndCreateFailureResult(
  CommandEnvironment env, String message, Code detailedCode) {
- if (message.charAt(message.length() - 1) != '.') {
- message = message.concat(".");
- }
  String fullMessage =
  String.format(
- message.concat(" Type '%s help mod' for syntax and help."),
- env.getRuntime().getProductName());
+ "%s%s Type '%s help mod' for syntax and help.",
+ message, message.endsWith(".") ? "" : ".", env.getRuntime().getProductName());
  env.getReporter().handle(Event.error(fullMessage));
  return createFailureResult(fullMessage, detailedCode);
  }