Disable performance tests

[npolshakova]

Description

Disable performance tests in OSS.

API changes

NONE

Code changes

NONE

CI changes

• Disable automatic nightly performance tests
• Keep manual CI performance trigger, but bump image
• Add instructions for running performance tests locally.

Docs changes

NONE

Context

k8sgateway#10369 (comment)

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

BOT NOTES:
resolves k8sgateway#10369

[solo-changelog-bot]

Issues linked to changelog:
k8sgateway#10369

[github-actions]

Visit the preview URL for this PR (updated for commit 9bd755b):

https://gloo-edge--pr10425-npolshak-disable-per-4rtq5fno.web.app

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