Add response body size limitation to mitigate memory usage risks.

Currently, IIUC, the http transport for the OTLP exporters does not limit the amount of data read on the response:

Refer to open-telemetry/opentelemetry-proto#781
This recommends limiting to 4MiB (uncompressed).

Notes:

• I haven't yet looked into the fetch transport (https://github.com/open-telemetry/opentelemetry-js/blob/main/experimental/packages/otlp-exporter-base/src/transport/fetch-transport.ts) used by the browser exporter.