lib-sieve: sieve-actions - Add "last" parameter to action finish method.

src/lib-sieve/plugins/duplicate/ext-duplicate-common.c

src/lib-sieve/sieve-actions.h

src/lib-sieve/sieve-result.c

src/lib-sieve/sieve-result.h

src/lib-sieve/sieve.c

src/testsuite/testsuite-result.c