proposal: x/debug: move core and gocore out of internal

[ajwerner]

viewcore has the capacity to be an invaluable tool but has some rough edges. Nevertheless, it'll never have all of the functionality for core dump analysis users might want. Forcing users to hack from within the debug repo is not likely to spur innovation in this area. The primary libraries driving that tool are underneath and internal directory which prevents the community from leveraging them to build out new tools. Let's fix that.

I've heard through the grapevine that these libraries weren't intended to be left unexposed forever. cc @randall77.

[dominikh]

This can probably be closed in favour of the more detailed #57447.

[rsc]

This proposal is a duplicate of a previously discussed proposal, as noted above,
and there is no significant new information to justify reopening the discussion.
The issue has therefore been declined as a duplicate.
— rsc for the proposal review group