Ensure all type assertion are checked

[amyangfei]

Feature Request

Is your feature request related to a problem? Please describe:

such as the bug in #2758, type assertion without any check can lead to unexpected panic

Describe the feature you'd like:

• Ensure all type assertion is checked, we found many type assertions in codec module.
• Investigate whether there is any lint way to detect unchecked type assertion.

cdc/sink/codec/avro.go:397:             str := col.Value.(string)
cdc/sink/codec/avro.go:429:             str := col.Value.(string)
cdc/sink/codec/avro.go:475:             return col.Value.(int64), "long", nil
cdc/sink/codec/avro.go:477:             return col.Value.(tijson.BinaryJSON).String(), "string", nil
cdc/sink/codec/avro.go:479:             return col.Value.(string), "string", nil
cdc/sink/codec/avro.go:488:                     return int32(col.Value.(uint64)), "int", nil
cdc/sink/codec/avro.go:490:             return int32(col.Value.(int64)), "int", nil
cdc/sink/codec/avro.go:493:                     return int64(col.Value.(uint64)), "long", nil
cdc/sink/codec/avro.go:495:             return col.Value.(int64), "int", nil
cdc/sink/codec/avro.go:500:             return col.Value.(int64), "long", nil
cdc/sink/codec/avro.go:502:             return col.Value.(float64), "float", nil
cdc/sink/codec/maxwell.go:105:                                  value.Old[v.Name] = string(v.Value.([]byte))
cdc/sink/codec/maxwell.go:120:                                  value.Data[v.Name] = string(v.Value.([]byte))
cdc/sink/codec/maxwell.go:142:                                          if value.Data[v.Name] != string(v.Value.([]byte)) {
cdc/sink/codec/maxwell.go:143:                                                  value.Old[v.Name] = string(v.Value.([]byte))
cdc/sink/codec/json.go:67:              str := string(col.Value.([]byte))
cdc/sink/codec/json.go:89:              str := col.Value.(string)
cdc/sink/producer/kafka/kafka.go:251:                   flushedOffset := msg.Metadata.(uint64)
cdc/sink/common/flow_control.go:209:            if peeked := c.queue.Front().(*commitTsSizeEntry); peeked.CommitTs <= resolvedTs {
cdc/model/reactor_state.go:298:         return fn(e.(*ChangeFeedInfo))
cdc/model/reactor_state.go:313:         return fn(e.(*ChangeFeedStatus))
cdc/model/reactor_state.go:329:         return fn(e.(*TaskPosition))
cdc/model/reactor_state.go:345:         return fn(e.(*TaskStatus))
cdc/model/reactor_state.go:361:         return fn(*e.(*TaskWorkload))
cdc/entry/mounter.go:280:       k := meta.(metaListData)
cdc/processor/manager.go:80:    ctx := stdCtx.(cdcContext.Context)
cdc/processor/manager.go:81:    globalState := state.(*model.GlobalReactorState)
cdc/processor/manager.go:184:           w := cmd.payload.(io.Writer)

[overvenus]

@zhaoxinyu PTAL