Fix Field.java documentation to refer to new IntField/FloatField/LongField/DoubleField

[rmuir]

Description

Currently Field.java has these docs:

/**
 * Expert: directly create a field for a document. Most users should use one of the sugar
 * subclasses:
 *
 * <ul>
 *   <li>{@link TextField}: {@link Reader} or {@link String} indexed for full-text search
 *   <li>{@link StringField}: {@link String} indexed verbatim as a single token
 *   <li>{@link IntPoint}: {@code int} indexed for exact/range queries.
 *   <li>{@link LongPoint}: {@code long} indexed for exact/range queries.
 *   <li>{@link FloatPoint}: {@code float} indexed for exact/range queries.
 *   <li>{@link DoublePoint}: {@code double} indexed for exact/range queries.
 *   <li>{@link SortedDocValuesField}: {@code byte[]} indexed column-wise for sorting/faceting
 *   <li>{@link SortedSetDocValuesField}: {@code SortedSet<byte[]>} indexed column-wise for
 *       sorting/faceting
 *   <li>{@link NumericDocValuesField}: {@code long} indexed column-wise for sorting/faceting
 *   <li>{@link SortedNumericDocValuesField}: {@code SortedSet<long>} indexed column-wise for
 *       sorting/faceting
 *   <li>{@link StoredField}: Stored-only value for retrieving in summary results
 * </ul>

I think it would be better to bring this up-to-date. We can at least replace IntPoint, LongPoint, FloatPoint, and DoublePoint with IntField, LongField, FloatField, and DoubleField.

Each one of these classes also documents/links you to look at more expert classes (e.g. IntPoint, SortedNumericDocValuesField, StoredField) if you want expert control.

But it would be better to point the user to these new easier-to-use field subclasses.

[Harshitha-g-06]

@rmuir Hi, may I work on this task?