…ersisted CDC offset (#63219)

### What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

PG streaming jobs with a temporal chunk-key column (e.g. `DATE` PK) fail
during snapshot read with:

```
PSQLException: ERROR: operator does not exist: date <= character varying
  Hint: No operator matches the given name and argument types.
```

**Root cause**

cdc_client reports snapshot splits to FE; FE persists the offset as JSON
via Spring Jackson, where `SqlDateSerializer` writes `java.sql.Date` as
a `"yyyy-MM-dd"` string. When the offset is later read back,
`ObjectMapper.convertValue(offset, SnapshotSplit.class)` lands the bound
values back into `Object[]` as `String` (type info is gone). At read
time `PostgresQueryUtils.readTableSplitDataStatement` calls bare
`statement.setObject(idx, splitEnd[i])`; PG JDBC sends `String` as
VARCHAR oid, and PostgreSQL — strict about operator resolution — refuses
`date <= varchar` (no implicit cast from varchar to date).

The same FE round-trip happens for MySQL too. MySQL server is lenient
enough to implicitly coerce the bound, so the surface error does not
appear, but `SplitKeyUtils.compareObjects` falls back to `toString()`
comparison whenever the restored type doesn't match the Debezium
connect-schema type — a latent issue worth keeping consistent.

**Fix**

Restore the original Java types at the cdc_client side, where the loss
happens:

- `AbstractCdcSourceReader` adds:
- abstract `probeSplitKeyClass(TableId, Column, JobBaseConfig)` —
dialect-specific lookup
- `resolveSplitKeyClass(...)` — per-column cached wrapper (1 probe per
table.column, reused across splits)
- static `convertBounds(Object[], Class<?>, ObjectMapper)` — restores
Object[] elements to the target class
- `PostgresSourceReader` / `MySqlSourceReader` override
`probeSplitKeyClass`: run `SELECT col FROM table WHERE 1=0` and use
`ResultSetMetaData.getColumnClassName(1)` so the JDBC driver itself
decides the Java type. Probe failure throws (no silent fallback — silent
fallback would let the original bug recur).
- `JdbcIncrementalSourceReader.createSnapshotSplit` /
`createStreamSplit` and `MySqlSourceReader.createSnapshotSplit` /
`createBinlogSplit` (4 sites total) apply `convertBounds` before
constructing Flink CDC's `SnapshotSplit` / `FinishedSnapshotSplitInfo`.
- `convertBounds` special-cases `java.sql.Date` / `Timestamp` / `Time`
via `valueOf` to match the JVM-default-TZ semantics of `rs.getObject`
(Jackson's default `SqlDateDeserializer` hard-codes GMT, which would
shift the value in non-UTC TZs). Other types fall through to
`ObjectMapper.convertValue`.

### Release note

Fix PG/MySQL streaming snapshot failing on temporal chunk-key columns
after FE offset JSON round-trip strips the original Java type.