[tsp-client] Upgrade minimum node versions for import.meta.resolve()

[mikeharder]

The following PR added a call to import.meta.resolve(), which is only available starting with Node 18.19.0 and 20.6.0:

f5d5955#diff-6f62171ec5df7a0f474274b3d6aed40ffebe0ff3f78c0ef749dc8f315b777107R58

On older Node versions, tsp-client now fails with this error:

TypeError: (intermediate value).resolve is not a function

To address this, the minimum node versions should be incremented, so consumers get a better error message:

npm WARN EBADENGINE Unsupported engine {
npm WARN EBADENGINE   package: '@azure-tools/[email protected]',
npm WARN EBADENGINE   required: { node: '^18.19.0 || >=20.6.0' },
npm WARN EBADENGINE   current: { node: 'v18.18.2', npm: '9.8.1' }
npm WARN EBADENGINE }