Don't try to read from the early console if EarlyBootDmesg is disabled

[OneBlue]

Summary of the Pull Request

PR Checklist

This change updates the dmesg collector to not try to read from the early boot serial if early boot logging is disabled.

This avoids creating an essentially useless thread, and this error when the session terminates:

Microsoft.Windows.Wsla	Error	01-30-2026 17:12:19.969	"HRESULTString: 	E_ABORT
code: 	E_ABORT
failurecount: 	1
functon: 	wsl::windows::common::helpers::ConnectPipe
hr: 	0x80004004

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Pull request overview

This PR updates the WSLA VM boot path so that the dmesg collector only attaches to the early-boot serial console when early boot logging is actually enabled, avoiding unnecessary thread creation and expected E_ABORT errors on shutdown.

Changes:

• Passes FeatureEnabled(WslaFeatureFlagsEarlyBootDmesg) into DmesgCollector::Create to conditionally enable the early boot console consumer instead of always enabling it.
• Keeps the existing FeatureEnabled(WslaFeatureFlagsEarlyBootDmesg) gating for kernel command line earlycon and COM1 configuration, maintaining consistency between producer and consumer of early boot logs.