Replaces every reference to the `amazon2023-latest-xlarge` distro on master with `amazon2023-latest-m6i-8xlarge`.

All 11 occurrences are in the two Streams variant files:

• `etc/evergreen_yml_components/variants/amazon/streams/streams_dev.yml` (`large_distro_name` expansions and per-task `distros` for `compile_and_archive_dist_test_TG` / `streams_build_and_push`)
• `etc/evergreen_yml_components/variants/amazon/streams/streams_release.yml` (same, plus `streams_build_debug`)

Pure string substitution; no other config changes.

The reason for this change is to increase the amount of RAM these hosts have available to reduce the risk of OOM errors.