test(targetTime): add E2E for PITR with targetTime specified in RFC3339 format - #8981

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/test feature_type=snapshot test_level=4

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/18881663420

Systematic failure for the PITR recovery with timestamp in RFC3339.
Matches the manual testing done in #8937

We're probably doing something wrong in func ConvertToPostgresFormat(timestamp string) string {, when doing conversion from RFC3339 / RFC3339, but not sure what it could be.

volume-snapshot-recovery-4-1392/cluster-pvc-snapshot-recovery-1-snapshot-recovery-jl6ws/snapshot-recovery.log:
{"level":"info","ts":"2025-10-28T16:40:20.32447612Z",
  "logger":"pg_ctl",
  "msg":"waiting for server to start....2025-10-28 16:40:20.324 UTC [38] LOG:  invalid value for parameter \"recovery_target_time\": \"2025-10-28 16:34:15.000000Z\"",
  "pipe":"stdout","logging_pod":"cluster-pvc-snapshot-recovery-1-snapshot-recovery"}

/test depth=push test_level=4 feature_type=snapshot

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/18901583886

/test depth=push test_level=4 feature_type=snapshot

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/18902898569

Changing the trailing Z from an RFC3339 stamp to +00 will make the recovery time setting work fine.

/test depth=push test_level=4 feature_type=snapshot

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/18904209250

Changing the trailing Z from an RFC3339 stamp to +00, and the separating space to T will make the recovery time setting work fine.

/test depth=push test_level=4 feature_type=snapshot

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/18905402935

/test depth=push test_level=4 feature_type=snapshot

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/18970112508

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/20616619827

/test depth=push test_level=4 feature_type=snapshot

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/20662695925

/test depth=push test_level=4 feature_type=snapshot

@jsilvela, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/21589251538