[javac] Add @MaxLength annotation for limiting lengths of string parameters (#8493)

Useful for eg OpModes, where names have a maximum length

Also includes validations for values in opmode annotations like
`@Autonomous(name = "...")`; name, group, and description all have
maximum allowable lengths

wpiannotations/src/main/java/org/wpilib/annotation/MaxLength.java

@@ -0,0 +1,46 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package org.wpilib.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Place on a method parameter of type String. Any string literals passed to that parameter will be
+ * checked at compile-time to be no longer than the maximum allowed length. Note that this cannot
+ * check dynamically generated string values - it is strongly recommended to pair this annotation
+ * with a runtime check to cover cases where dynamic values are used.
+ *
+ * <p>Errors generated by this annotation cannot be suppressed.
+ *
+ * <pre>{@code
+ * void acceptString(@MaxLength(5) String str) {
+ *   if (str.length() > 5) {
+ *     throw new IllegalArgumentException("String is too long");
+ *   }
+ *   // ...
+ * }
+ *
+ * acceptString("12345"); // OK - length is 5
+ * acceptString("123456"); // Compile-time error: length is 6
+ * acceptString("123" + "456"); // Compile-time error: length is 6
+ * acceptString(" ".repeat(16)); // Runtime error - string argument is not a literal
+ * }</pre>
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.PARAMETER)
+@Documented
+public @interface MaxLength {
+  /**
+   * The maximum allowable length of string literals passed to the annotated parameter. Must be a
+   * positive integer.
+   *
+   * @return The maximum length of allowed strings.
+   */
+  int value();
+}