Breaking Change: Running TypeScript on ES3 hosts no longer supported

[RyanCavanaugh]

#10270 uses APIs present only in ES5 runtimes to gain 15% speed and ~20% reduced memory usage.

This does not impact targeting ES3 hosts with --target ES3. The only scenario impacted is running the TypeScript compiler or language service on an ES3 host, which we believe to be very rare.

[DanielRosenwasser]

I thought I posted this at #10125?

[RyanCavanaugh]

Please search for duplicates before logging new issues.