FFM-11470 Fix analytics panic with nil target attributes

[erdirowlands]

What

The analytics code was refactored in #150 , and a nil check for target attributes was accidentally removed. This meant if an evaluation was made with a target with no attributes, we would dereference a nil pointer and a panic would occur when analytics are processed:

This PR:

• Adds a nil check before dereferencing target attributes

• Extracts out evaluation/target metrics processing code into separate methods, so that they can be unit tested

• Adds unit tests for the newly extracted methods, and sendDataAndResetCache

• Also retracts [v0.1.21, v0.1.22] due to this bug being critical and easily encountered.

• Bumps golang.org/x/net v0.25.0 for CVE-2023-45288

Testing

• New unit tests to verify that metrics are processed correctly, and a panic does not occur if attributes or anonymous is nil.
• New unit tests to verify that metrics are sent correctly.
• Manual integration test with prod2 account.
• TestGrid integration test.

[erdirowlands]

This is the nil check that was missing that would result in a panic.