[pg] Support work with `public.` prefix

[rekby]

https://github.com/ydb-platform/ydb/wiki/Local-run-postgres-tests

➤ echo "DROP TABLE t; CREATE TABLE public.t(id SERIAL PRIMARY KEY, val int);" | psql postgres://root:1234@localhost:5432/local
DROP TABLE
Status: GENERIC_ERROR
Issues:
<main>: Error: Error while parsing query.
    <main>:1:1: Error: Unknown cluster:

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➤ echo "DROP TABLE t; CREATE TABLE t(id SERIAL PRIMARY KEY, val int); SELECT pg_catalog.setval('public.t_id_seq', 3, true);" | psql postgres://root:1234@localhost:5432/local
Status: GENERIC_ERROR
Issues:
<main>: Error: Type annotation, code: 1030
    <main>:1:1: Error: At function: RemovePrefixMembers, At function: PgSelect, At function: PgSetItem, At function: PgResultItem
        <main>:1:8: Error: At function: PgCall
            <main>:1:8: Error: No access to proc: setval

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➤ echo "DROP SEQUENCE seq; CREATE SEQUENCE public.seq AS integer;" | psql postgres://root:1234@localhost:5432/local
Status: GENERIC_ERROR
Issues:
<main>: Error: Error while parsing query.
    <main>:1:1: Error: Unknown cluster:

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➤ echo "DROP TABLE t; DROP SEQUENCE t_id_seq; CREATE TABLE t(id integer NOT NULL, val integer, PRIMARY KEY(id)); CREATE SEQUENCE t_id_seq AS integer; ALTER TABLE ONLY public.t ALTER COLUMN id SET DEFAULT nextval('public.t_id_seq'::regclass);" | psql postgres://root:1234@localhost:5432/local
Status: GENERIC_ERROR
Issues:
<main>: Error: Error while parsing query.
    <main>:1:1: Error: Unknown cluster:

-----
➤ echo "DROP TABLE t; DROP SEQUENCE t_id_seq; CREATE TABLE t(id integer NOT NULL, val integer, PRIMARY KEY(id)); CREATE SEQUENCE t_id_seq AS integer; ALTER TABLE ONLY t ALTER COLUMN id SET DEFAULT nextval('public.t_id_seq'::regclass);" | psql postgres://root:1234@localhost:5432/local
Status: SCHEME_ERROR
Issues:
<main>: Error: Check failed: path: '/local/public.t_id_seq', error: path hasn't been resolved, nearest resolved path: '/local' (id: [OwnerId: 72075186232723360, LocalPathId: 1]), code: 2003
<main>: Error: Query invalidated on scheme/internal error during Scheme execution, code: 2019