Remove deprecated JSON reporting from P3A

[DJAndries]

In addition, remove Constellation and Nebula feature guards, as they are already enabled for all users.

[GeetaSarvadnya]

Verification PASSED on

Brave | 1.81.102 Chromium: 138.0.7204.49 (Official Build) beta (64-bit)
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Revision | 3d801bb52eb13933b38f4f4b334af102e3285df6
OS | Windows 10 Version 22H2 (Build 19045.5965)

• Verified the test plan from Remove JSON and P2A reporting from P3A brave-core#29508

Step 2_PASSED

1. Confirmed that requests are being made to star-randsrv.bsg.brave.com to prepare Constellation metrics
2. Confirmed that the URL path is /instances/<cadence type>/randomness
3. Confirmed that when one request is sent for a particular cadence, check to see that metrics are being marked as "sent" as they are being sent to the server, by checking the correct "logs" object in local state.

53 randomness requests are sent to this endpoint star-randsrv.bsg.brave.com

Step 1,2	Step 1, 2(1)	Step 1, 2(2)	Step 1, 2(2)

4. There are 36 metrics are listed under logs_constellation_prep shown in the images below Step 4(1), Step 4(2) and Step 4(3)
   All the metrics under Logs and logs_constellation_prep are marked as sent:true, when we look at the https://star-randsrv.bsg.brave.com endpoint at the server, 36 typical metrics are sent to the server in the form of randomness instances as shown in the images above Step 1,2 and Step 1,2(1)

36 metrics are shown under logs_constellation_prep

Step 4(1)	Step 4(2)	Step 4(3)

5. Confirmed that no. of metrics shown under logs_constellation_prep_express via brave://local-state are same as the no. of metrics shown under star-randsrv.bsg.brave.com server endpoint as expected

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6. Confirmed that no. of metrics shown under logs_constellation_prep_slow via brave://local-state are same as the no. of metrics shown under star-randsrv.bsg.brave.com server endpoint as expected

Step 3_PASSED

Ensure final measurements are being sent to collector.bsg.brave.com. The URL path should be /<cadence type>. Before metrics are sent to this server, they should appear under constellation_logs, constellation_logs_express and constellation_logs_slow after being prepared (from the requests being made in step 2). As soon as the metrics are sent to the collector, the metric should disappear in the relevant local state object.

1. Confirmed that, before the metrics are sent to server they are prepared to sent and hence appear under logs_constellation_prep_express, logs_constellation_prep_slow and logs_constellation_prep after that the metrics are appear under constellation_logs, constellation_logs_express and constellation_logs_slow .
   But the metrics listed under constellation_logs, constellation_logs_express and constellation_logs_slow are removed once the metrics are sent to the server

metrics prepared

Example	Example	Example	Example	Example

constellation logs

2. Confirmed that the final measurements are sent to the endpoint collector.bsg.brave.com
   • 8 slow metrics are sent to the endpoint collector.bsg.brave.com as expected
   • 9 express metrics are sent to the endpoint collector.bsg.brave.com
   • There are two creative cadence type metrics are sent to the endpoint collector.bsg.brave.com which is expected as two creative metrics shown under logs_constellation_prep_express block
   • There are 36 typical metrics are sent to the endpoint collector.bsg.brave.com as there are 36 typical metrics are listed under Logs in brave://local-state file

Example	Example

[GeetaSarvadnya]

@DJAndries: I have verified the test plan on 1.81.102. I don't see the endpoints star-randsrv.bsg.brave.com and collector.bsg.brave.com reported via Charles proxy. Can you verify the test plan again? Thanks!