[Security Solution] Threshold Rules' Timeline Templates are not respected during investigation

[rylnd]

Describe the bug:
If a user applies a timeline template to a Threshold rule, its settings will not be applied when those rule's alerts are investigated in Timeline.

Kibana/Elasticsearch Stack version:
8.3.0; likely earlier

Steps to reproduce:

1. Create a custom timeline template with custom columns
2. Apply the timeline template to a threshold rule
3. Click "Investigate in timeline" on a generated threshold alert

Current behavior:
The columns and other timeline template configuration are not applied to the threshold alert timeline

Expected behavior:
Timeline templates are supported (as much as possible) along with the special threshold timeline rendering

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[rylnd]

@madirey are there any Timeline behaviors specific to Threshold alerts that would conflict with timeline template configuration? I think that's the only potential wrinkle here.

[rylnd]

Related: #129966

[ghost]

Hi Team,

We have validated this issue on 8.4.0 BC1 build and observed that issue is Fixed 🟢

• Custom columns are displaying when click on "Investigate in timeline" on a generated threshold alert

Please find the below testing Details:

Build info

VERSION : 8.4.0 BC1
Build: 54999
COMMIT: 58f7eaf0f8dc3c43cbfcd393e587f155e97b3d0d

Screenshot/Screencast

threshold.mp4

Hence, We are marking as QA Validated!!

cc: @MadameSheema

Thanks!!