RHOAIENG-9230 Restructure InitSegment

[pilhuhn]

Restructure InitSegment
https://issues.redhat.com/browse/RHOAIENG-9230

Description

Split off Segment initialisation from usage.
Remove username from init code and only use when needed to fire an identify event.
No user-visible changes.

How Has This Been Tested?

Manual test by looking at browser console

Request review criteria:

Self checklist (all need to be checked):

• The developer has manually tested the changes and verified that the changes work
• Commits have been squashed into descriptive, self-contained units of work (e.g. 'WIP' and 'Implements feedback' style messages have been removed)
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has added tests or explained why testing cannot be added (unit or cypress tests for related changes)

After the PR is posted & before it merges:

• The developer has tested their solution on a cluster by using the image produced by the PR to main

cc @andrewballantyne

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

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