Fix heap-size writing unrecognized hw.heapSize property

[jramism]

Problem

The heap-size input is written to the AVD's config.ini as hw.heapSize:

if (heapSize) {
  configEntries.push(`hw.heapSize=${heapSize}`);
}

hw.heapSize is not a recognized AVD hardware property, so the value is
ignored and heap-size has no effect on the emulator.

The property that actually sets the per-app VM heap is vm.heapSize, as
defined in the SDK's emulator/lib/hardware-properties.ini:

name        = vm.heapSize
type        = integer
abstract    = Max VM application heap size
description = The maximum heap size a Dalvik application might allocate
              before being killed by the system. Value is in megabytes.

Fix

Write vm.heapSize instead of hw.heapSize. hw.ramSize (used for the
ram-size input) is already the correct property name and is left unchanged.

Related: #188

Notes

• Only src/emulator-manager.ts and the compiled lib/emulator-manager.js
  change, matching the repo convention of committing both.
• The change is a single token inside a template literal, so the compiled
  output is identical to tsc's.