[ISSUE-776] add selectFrom spec

[kihwankim]

Motivation

• queryDSL's selectFrom function

Modifications

• add selectFrom spec in kotlinJdsl

Result

• Users no longer need to call the select() and from() functions respectively when they query one entity information

       authorRepository.findAll {
            selectFrom(
                entity(Author::class),
                leftJoin(BookAuthor::class).on(path(Author::authorId).equal(path(BookAuthor::authorId))),
            ).where(
                path(BookAuthor::authorId).isNull(),
            ).orderBy(
                path(Author::authorId).asc(),
            )
        }

Closes

• #776