Log redact on TiFlash and PD (4.0) (pingcap#4997) (pingcap#5000)

* cherry pick pingcap#4997 to master

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

* change 4.0.10 to 5.0.0-rc

* Update tiflash/tiflash-configuration.md

Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com>

tiflash/tiflash-configuration.md

@@ -165,6 +165,11 @@ delta_index_cache_size = 0
     # cert_path = "/path/to/tiflash-server.pem"
     ## Path of the file that contains X509 key in PEM format.
     # key_path = "/path/to/tiflash-server-key.pem"
+
+    ## New in v5.0.0-rc. This configuration item enables or disables log redaction. If the configuration value
+    ## is set to `true`, all user data in the log will be replaced by `?`.
+    ## Note that you also need to set `security.redact-info-log` for tiflash-learner's logging in tiflash-learner.toml.
+    # redact_info_log = false
 ```
 
 ### Configure the `tiflash-learner.toml` file
@@ -184,7 +189,7 @@ delta_index_cache_size = 0
     ## If you set it to 0ms, the optimization is disabled.
     store-batch-retry-recv-timeout = "4ms"
 [security]
-    ## New in v4.0.10. This configuration item enables or disables log redaction.
+    ## New in v5.0.0-rc. This configuration item enables or disables log redaction.
     ## If the configuration value is set to true,
     ## all user data in the log will be replaced by ?. The default value is false.
     redact-info-log = false