feat: add composable annotation support and meta-annotation processing

[bengbengbalabalabeng]

Purpose of the pull request

As title.

Related: #918
Closed: #920 (previous development draft)

What's changed?

1. Introduce two meta-annotations, @FesodMarked and @FesodMarked.AliasFor, to expand the Target - ElementType#ANNOTATION_TYPE restriction scope for other internal annotations except @ExcelIgnore and @ExcelIgnoreUnannotated, making it convenient for users to define custom combined annotations (Included third-party annotations).
2. Added AnnotatedElementUtils utility class to handle composable-annotations lookup.
3. Wire the lookups into ClassUtils and ExcelWriteHeadProperty, covering both read and write paths; behavior of directly-declared annotations is unchanged.
4. Added introduction document.

Example

// Define
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@FesodMarked
@ExcelProperty
@ColumnWidth(20)
public @interface TitledColumn {

    @FesodMarked.AliasFor(annotation = ExcelProperty.class, attribute = "value")
    String title() default "";
}

// Use
// Same as:
// @ExcelProperty(value = {"NAME"})
// @ColumnWidth(value = 20)
@TitledColumn(title = "NAME")
private String name;

Precedence and Override Rules

(Detailed examples are provided in annotation.md; only the core rules are listed here.)

• Annotation Level: Directly declared target annotation > Composed annotation. The directly declared target annotation wins entirely, and any matching target annotation inside composed annotations is completely ignored.
• Composed Annotation Attribute Level: Within an active composed annotation, @FesodMarked.AliasFor values (including defaults) > Static preset values.

Checklist

• I have read the Contributor Guide.
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.