fix: restore protected modifier on relayCreationTimeoutMs in test helper

[NikolaRHristov]

Same as #310195 as we're running into:

[19:19:00] [mangler] Done collecting. Classes: 10966. Exported symbols: 13574
[19:19:01] [mangler] WARN: 'relayCreationTimeoutMs' from src/vs/platform/agentHost/node/sshRemoteAgentHostService.ts:520 became PUBLIC because of: src/vs/platform/agentHost/test/node/sshRemoteAgentHostService.test.ts:177
[19:19:01] [mangler] ERROR: Protected fields have been made PUBLIC. This hurts minification and is therefore not allowed. Review the WARN messages further above
[19:19:01] Starting compilation...
[19:19:01] 'compile-build-with-mangling' errored after 14 s
[19:19:01] Error: Protected fields have been made PUBLIC. This hurts minification and is therefore not allowed. Review the WARN messages further above
    at Mangler.computeNewFileContents (file://build/lib/mangle/index.ts:568:10)
    at task (file://build/lib/compilation.ts:144:47)
    at file://build/lib/task.ts:62:22
    at new Promise (<anonymous>)
    at _doExecute (file://build/lib/task.ts:50:9)
    at _execute (file://build/lib/task.ts:40:8)
    at result (file://build/lib/task.ts:85:10)
    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)
    at async _execute (file://build/lib/task.ts:40:2)
    at async result (file://build/lib/task.ts:85:4)

after npm install -> npm run compile-build

[NikolaRHristov]

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[Copilot]

Pull request overview

This PR aims to fix compile-build-with-mangling failures by preventing the mangler from promoting SSHRemoteAgentHostMainService.relayCreationTimeoutMs to public due to a public override in the test subclass.

Changes:

• Change TestableSSHRemoteAgentHostMainService.relayCreationTimeoutMs from override (effectively public) to protected override to match the base class and avoid mangler promotion errors.

[NikolaRHristov]

A follow up, as we now encountered:

error TS2445: Property 'relayCreationTimeoutMs' is protected and only accessible within class 'TestableSSHRemoteAgentHostMainService' and its subclasses.

1020   service.relayCreationTimeoutMs = 50;
               ~~~~~~~~~~~~~~~~~~~~~~

so an additional commit was made specifically for the test - c5061c3