add buffer.transcode to nodejs_compat

[anonrig]

This pull-request adds require('node:buffer').transcode() support. It uses ICU for most encodings, and simdutf for latin1, utf8 and utf-16 operations.

few nits to address

[jasnell]

Adding the "needs-internal-pr" label on this to ensure that we make certain that the internal CI run is green before this lands. Once the internal CI comes back green with this change, the label can be removed and the PR can be merged

[anonrig]

Internal PR is now resolved. We can merge this now.