[SEC-22123] Update TF Provider Edit Default rule with custom fields.

[cpatel24]

Update TF Provider Edit Default rule with custom fields.

Testing Terraform Provider

• Tested updating custom_query_extension, custom_name in https://dd.datad0g.com/security/configuration/siem/rules/edit/def-000-ouv through TF plan. It updated successfully.

Unit Test:

• Running tests locally passes fine:

$ RECORD=false TESTARGS="-run TestAccDatadogSecurityMonitoringDefaultRule_Basic" make testacc
  gotestsum --version || go install gotest.tools/gotestsum@latest
  gotestsum version dev
  which goimports || go install golang.org/x/tools/cmd/goimports@latest
  .
  .
  2025/06/25 00:08:12 DD_AGENT_HOST is not configured. Tests are executed without tracer and profiler.
  PASS datadog/tests.TestAccDatadogSecurityMonitoringDefaultRule_Basic (7.30s)
  PASS datadog/tests

$ RECORD=false TESTARGS="-run TestAccDatadogSecurityMonitoringDefaultRule_DeprecationWarning" make testacc
  gotestsum --version || go install gotest.tools/gotestsum@latest
  .
  .
  2025/06/25 00:07:51 DD_AGENT_HOST is not configured. Tests are executed without tracer and profiler.
  PASS datadog/tests.TestAccDatadogSecurityMonitoringDefaultRule_DeprecationWarning (6.62s)
  PASS datadog/tests

[jhgilbert]

Approved with one comment, thanks!