[browser] Remove check for user agent when attaching debugger

[maraf]

• Remove check for user agent when attaching debugger
• Attach debugger only when DebugLevel != 0
• Don't zero debug level when there are no PDBs in config (embedded PDB can be used)

Fixes #104234

[thaystg]

I don't like this check for PDB to decide the debug level because the customer should be able to use embedded pdbs?
Am I understanding the code wrongly?

[pavelsavara]

I think that this change enables debugging on NodeJS, could you please test that it also works ?

[maraf]

could you please test that it also works ?

No, managed debugging doesn't work on NodeJS

[lewing]

@maraf this appears to have turned off all optimizations on v8? dotnet/perf-autofiling-issues#39876