Simplify the toolchain

[vicary]

Recent renovate PRs have breaking tests, which is ultimately caused by the gradual transitioning towards ESM from upstream dependencies.

When fixing these errors, I found the current toolchain a bit cumbersome and requires more maintenance than I am comfortable with.

The main goal of this issue is to replace existing tools with as many zero-conf services as possible, and prefer more actively maintained dependencies when multiple options are present.

1. renovatebot -> dependabot
2. changesets -> semantic-release with Nx
   Major version released on patch changes changesets/action#381
3. size-limit -> andresz1/size-limit-action
4. jest et al. -> vitest
   1. jest needs humongous amount of configurations to deal with a hybrid of CJS and ESM of deps. Also partial transformIgnorePatterns are really slow, bringing 2-3s tests to 10s locally and >30s on CI.
   2. On the other hand, the Deno + DNT stack is promising but lacks dependabot support.
5. bob-tsm -> tsup
6. graphql-ez et al. -> graphql-yoga + @graphql-tools/mock
   More actively maintained alternatives.
7. Simplify file structure
   1. Remove scripts/* and transition to an ESM-first codebase
   2. Remove internal/*
      1. Move internal/images to assets/
      2. Rewrite internal/test-utils into @gqty/testing to prepare for a public mocking solution
      3. Replace all jest usage with vitest, with minimal configuraitons.

[vicary]

Waiting for a complete toolchain before moving on towards a ESM-first repo:

1. Node

   1. Build: Requires porting to a delicate esbuild setup
   2. Test: Requires porting to vitest
   3. Workspace: pnpm
   4. Release: changeset
   5. SCA: dependabot & renovate

2. Bun

   1. Build: bun build
   2. Test: bun test
   3. Workspace
   4. Release: changeset is pnpm friendly, not the best DX with Bun
   5. SCA: dependabot still requires enable-beta-ecosystems: true

3. Deno

   1. Build: DNT
   2. Test: deno test
   3. Workspace
   4. Release: package.json > deno.json?
   5. SCA: A cusotm pipeline with @deno/bump-workspaces
      dependabot Dependabot support/integration denoland/deno#26788 (comment)