feat: Adding performance timers to navigation

[nickrandolph]

PR Type

What kind of change does this PR introduce?

• Feature

What is the current behavior?

No way to time how long navigation takes

What is the new behavior?

Define UNO_EXT_TIMERS in csproj or Directory.Build.info to enable performance timers

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Docs have been added/updated which fit documentation template. (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Wasm UI Tests are not showing unexpected any differences. Validate PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Updated the Release Notes
• Associated with an issue (GitHub or internal)

Other information

Internal Issue (If applicable):