Extract LibsqlBlob and LibsqlClob from LibsqlResultSet #199

Goal

Move the read-only Blob and Clob implementations out of LibsqlResultSet. They are two static nested classes of about 204 lines that never touch the enclosing instance or the cursor.

Depends on

#198. Same file, so this runs after the REAL formatter moves.

Pin

LibsqlResultSetTest covers getBlob and getClob values, NULL streams, and byte and character stream parity. The upstream ResultSetTest exercises the LOB paths.

Scope

• Create package-private top-level LibsqlBlob and LibsqlClob from LibsqlResultSet 1293 to 1497.
• Keep the package-private constructors used by getBlob (944) and getClob (948).

Preserve

• The read-only and freed exception messages, and the position and length validation messages.
• free() nulls the backing bytes or text.
• LibsqlClob.getAsciiStream() uses US_ASCII.

Acceptance

• LibsqlBlob.java and LibsqlClob.java exist and hold the moved code unchanged.
• LibsqlResultSet.java is under 1050 lines.
• ./mvnw -pl libsql-jdbc -am test green with no assertion edited.
• ./mvnw spotless:check green.