[CDCSDK] Enforce relationship between CDC retention gflags

[es1024]

Jira Link: DB-10503

Description

We currently have a pair of gflags: cdc_wal_retention_time_secs and cdc_intent_retention_ms, but implicitly require that cdc_intent_retention_ms <= cdc_wal_retention_time_secs. This should be made explicit in code (error check/using appropriate values when not true).

Source connector version

n/a

Connector configuration

n/a

YugabyteDB version

No response

Issue Type

kind/bug

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[rthallamko3]

cc @hari90 , @suranjan

[hari90]

This needs a flag callback on both flags that will FATAL if the incorrect value is set. cc @suranjan as its cdcsdk only