fix(frontend): Include CSRF token value in beacon call

[Ralkion]

SUMMARY

Before sending the log beacon call, include the CSRF token if it exists.

TESTING INSTRUCTIONS

1. Be sure that CSRF is enabled
2. Navigate the site and watch logs
3. Verify that the POST /superset/log messages are 200s and not 302s.

ADDITIONAL INFORMATION

• Has associated issue: Error logs full of "CSRF token missing" on POST /superset/log #30717
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[Ralkion]

I see the failed frontend test. I'll fix the existing and create a new one specific to this case a little later today.

[Ralkion]

@rusackas unit tests passed. Ready to go.

[Ralkion]

Hold off on this, I'm just discovering that it could actually be an issue in our configuration.

Seems by default the WTF_CSRF_EXEMPT_LIST is

[
    "superset.views.core.log",
    "superset.views.core.explore_json",
    "superset.charts.data.api.data",
    "superset.dashboards.api.cache_dashboard_screenshot",
]

But for some reason ours was defined to be []. I may have been looking in the wrong place.

[Ralkion]

Confirming that the issue was actually a misconfiguration on our end. I'll close this PR.