[browser] prevent <DebuggerSupport> from disabling interp optimizations (#85792)

[browser] prevent <DebuggerSupport> from disabling interp optimizations (#85792)

* [wasm] Don't enable debugging for library tests by default

@pavelsavara and @brzvlad found that some tests like
System.Collections.Immutable.Tests run slower because the runtime has
debugging enabled which causes the interpreter to disable optimizations.

Reason:

- Some tests depend on debugger attributes, and thus set
  `$(DebuggerSupport)=true` to preserve them while linking.
- Which sets `$(WasmDebugLevel)=-1`. But setting `$(WasmDebugLevel)<0`
  enables debugging support in the runtime.

- So, set this to `<0` only when building with `Configuration=Debug` .

* set it to zero only on CI

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Co-authored-by: Ankit Jain <radical@gmail.com>