lib-sieve: mime/foreverypart: Implemented loop nesting limit.

src/lib-sieve/plugins/mime/cmd-foreverypart.c

src/lib-sieve/sieve-interpreter.c

src/lib-sieve/sieve-interpreter.h

src/lib-sieve/sieve-limits.h

tests/extensions/mime/errors.svtest

tests/extensions/mime/errors/limits.sieve