[ci] Apply CFSClean environment settings

[jonathanpeppers]

Azure builds can make unnecessary public network requests for certificate revocation, SDK update checks, vulnerability auditing, telemetry, and implicit template restores. Centralize the relevant CI settings to keep these operations compatible with CFSClean network isolation.

• Apply the .NET revocation, workload notification, vulnerability audit, NuGet audit, and telemetry settings to both Azure pipeline entry points through the shared variables template.
• Set the repository-consumed RUNNINGONCI marker globally and remove its duplicate step-level definition so Maven and Gradle paths consistently use the configured dnceng mirrors.
• Add --no-restore to template creation because the generated projects are modified before their later build and restore.

Validation:

• Built tests/allpackages/AllPackagesTests.csproj and tests/extended/ExtendedTests.csproj.
• Parsed both pipeline entry points and the changed shared YAML templates.
• Confirmed git diff --check passes.

[Copilot]

Pull request overview

Centralizes CI environment settings to reduce unwanted outbound network activity (revocation checks, update notifications, vulnerability/audit checks, telemetry, and template-triggered restores) so Azure builds remain compatible with CFSClean network isolation.

Changes:

• Added shared CI variables to disable .NET revocation checks, workload update notifications, SDK vulnerability checks, NuGet audit, and telemetry; also set RUNNINGONCI globally.
• Removed the redundant step-level RUNNINGONCI env override from the CI build-and-test template.
• Updated extended/allpackages tests to run dotnet new with --no-restore, deferring restore until after project modifications.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tests/extended/TestAllIndividualPackages.cs	Uses dotnet new ... --no-restore to avoid early restores before project edits.
tests/allpackages/TestAllIndividualPackages.cs	Same --no-restore change for the all-packages test project creation flow.
build/ci/variables.yml	Centralizes CI env/variables for revocation, workload notifications, vulnerability checks, NuGet audit, telemetry, and RUNNINGONCI.
build/ci/build-and-test.yml	Removes duplicate per-step RUNNINGONCI now that it’s set globally.

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[jonathanpeppers]

@dalexsoto review

[dalexsoto]

The shared CFSClean environment settings and no-restore template flow propagate correctly without breaking later restores or tests.