fix: cosmic-proto exports through npm

[turadg]

Description

#6540 didn't solve for NPM consumers that don't support export maps.

This puts files in swingset instead of symlinks, so they go through npm pack. It re-exports instead of copying because the source code needs to be able to reference ../cosmos and having that in the second path would require copying that directory too.

Security Considerations

Documentation Considerations

Testing Considerations

❯ npm pack
npm notice
npm notice 📦  @agoric/cosmic-proto@0.2.1
npm notice === Tarball Contents ===
npm notice 11.4kB LICENSE
npm notice 352B   README.md
npm notice 18.0kB dist/agoric/swingset/msgs.d.ts
npm notice 17.9kB dist/agoric/swingset/msgs.js
npm notice 14.0kB dist/agoric/swingset/query.d.ts
npm notice 9.6kB  dist/agoric/swingset/query.js
npm notice 16.3kB dist/agoric/swingset/swingset.d.ts
npm notice 17.0kB dist/agoric/swingset/swingset.js
npm notice 3.3kB  dist/cosmos/base/v1beta1/coin.d.ts
npm notice 6.1kB  dist/cosmos/base/v1beta1/coin.js
npm notice 1.8kB  package.json
npm notice 90B    swingset/msgs.js
npm notice 91B    swingset/query.js
npm notice 94B    swingset/swingset.js
npm notice === Tarball Details ===
npm notice name:          @agoric/cosmic-proto
npm notice version:       0.2.1
npm notice filename:      @agoric/cosmic-proto-0.2.1.tgz
npm notice package size:  16.6 kB
npm notice unpacked size: 116.1 kB
npm notice shasum:        a5ccc3df532c938d4bfe06e1b870117e4c436465
npm notice integrity:     sha512-nphByyltyAeaQ[...]tQCs/SLkD0rQg==
npm notice total files:   14

(The swingset files are there)

[dckc]

a smoke test showed this works