Revert "user anchor for serialization (#6)"

[arielsegura]

This reverts commit 2aa04d3.

We got too many problems with Anchor:

• Artifact not deployed in npm Publish ts/spl-governance to npm coral-xyz/anchor#2203
• The library simply does not work on browsers Runtime errors in browser coral-xyz/anchor#1638
• Doesn't work with webpack 5 (therefore react scripts 5). This is a constraint we would add to the library, only because anchor has this problem and it's clearly not a priority for them, as they only offer the workaround of downgrading to webpack 4.
  See ts: Installing @project-serum/anchor 0.20.1 on client crash due to missing module assert  coral-xyz/anchor#1290 and Incompatible with current react-scripts (v5.0.0) while using create-react-app  coral-xyz/anchor#1318
• Some types are not exported and the development experience is not the best (i.e. missing autocompletion)

In addition to that, Anchor doesn't seem to be very responsive on the issues/PRs, and I even submitted a PR that got zero reviews even though I asked the maintainers on Discord to have a look coral-xyz/anchor#1700

It's unfortunate as Anchor seems to be a good library, but we have strong reasons to drop it for now.