`DelegatingAuthenticationFailureHandler` leaks implementation details in constructor

Describe the bug
The public constructor for DelegatingAuthenticationFailureHandler requires an instance of LinkedHashMap instead of accepting any Map implementation.

Expected behavior
APIs should take collections via the least specific interface, and not force specific implementations.

Suggested fix
Add a new constructor and deprecate the existing one:

public DelegatingAuthenticationFailureHandler(
        Map<Class<? extends AuthenticationException>, AuthenticationFailureHandler> handlers,
        AuthenticationFailureHandler defaultHandler) {
    Assert.notEmpty(handlers, "handlers cannot be null or empty");
    Assert.notNull(defaultHandler, "defaultHandler cannot be null");
    this.handlers = new LinkedHashMap(handlers);
    this.defaultHandler = defaultHandler;
}

If you need to force the caller to guarantee a defined iteration order, Java 21 added SequencedMap.

Start at the public constructors of DelegatingAuthenticationFailureHandler and inspect their validation and handler initialization. Add the Map-based API while deprecating the LinkedHashMap-based constructor, preserving existing behavior and accepting other Map implementations. Done means callers are no longer forced to provide LinkedHashMap and the existing validation remains intact.