eventservice: integrity behavior depends on the first registered changefeed

[lidezhu]

What did you do?

integrity-check-level is a changefeed-level configuration, but EventService creates one shared mounter per upstream cluster using the first registered dispatcher’s integrity config:

mounter: event.NewMounter(tz, integrity)

All later changefeeds on the same cluster reuse this mounter.

What did you expect to see?

Each changefeed should use its own integrity configuration.

What did you see instead?

As described above.

Versions of the cluster

Upstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):

(paste TiDB cluster version here)

Upstream TiKV version (execute tikv-server --version):

(paste TiKV version here)

TiCDC version (execute cdc version):

(paste TiCDC version here)