CmdPal: Adding a lock around perf monitor updates (#46061)

Based on reported bug in Teams.

Added lock around OnLoadBasePage._loadCount and modified
PerformanceWidgetPage to use Interlocked.Increment/Decrement on
_loadCount.

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Co-authored-by: leileizhang <[email protected]>
Co-authored-by: Niels Laute <[email protected]>
Co-authored-by: moooyo <[email protected]>
Co-authored-by: Yu Leng <[email protected]>
Co-authored-by: Kai Tao <[email protected]>
Co-authored-by: Jiří Polášek <[email protected]>
Co-authored-by: Shawn Yuan <[email protected]>
Co-authored-by: Gordon Lam <[email protected]>
Co-authored-by: Heiko <[email protected]>
Co-authored-by: Mike Hall <[email protected]>
Co-authored-by: vanzue <[email protected]>
Co-authored-by: Jaylyn Barbee <[email protected]>
Co-authored-by: Thanh Nguyen <[email protected]>
Co-authored-by: Zach Teutsch <[email protected]>