[release/9.0] Set network isolation policy for aspnetcore-ci

[github-actions]

Backport of #65168 to release/9.0

/cc @wtgodbe

Set network isolation policy for aspnetcore-ci

Summary of the changes (Less than 80 chars)

Description

{Detail}

Fixes #{bug number} (in this specific format)

Customer Impact

{Justification}

Regression?

• Yes
• No

[If yes, specify the version the behavior has regressed from]

Risk

• High
• Medium
• Low

[Justify the selection above]

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

---

When servicing release/2.3

• Make necessary changes in eng/PatchConfig.props

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[dotnet-policy-service]

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