Refactor/Improve some typings

Description

Commits

types: add remaining external typings

added @types/babelcore, @types/babeltraverse, and @types/lodash.merge and removed their declarations in env.d.ts
- also removed rollup-plugin-terser's declaration there because it has types built-in
- remaining actually don't have types per in-line comments
this improved type-checking allowed TS to do stricter checks and so exposed a few type errors that were fixed as well
- @rollup/plugin-babel depends on @types/babel__core as well, so the declaration here had previously overridden it
- custom had to be augmented as it's not an option of @rollup/plugin-babel
- passPerPreset did too though... it's not in @types/babel__core but it is a (deprecated) Babel option
  - logs seemed to show it was false regardless of what was passed in though...
- Rollup's plugins now started complaining that false wasn't a valid Plugin either, so added a .filter(Boolean) but that didn't fully fix it so had to type-cast

refactor/fix: consistently use capital TSDX everywhere

Jared had asked in a review comment back in December to consistently use capital TSDX (not tsdx) so this establishes that throughout the rest of the codebase
- I don't think any of these lines/files/variables were written by me, so I'm just fixing up existing ones
this came up as I was refactoring typings, so wanted to make sure everything was consistent as I went

refactor/types: explicitly name "at least one" types

refactor/types: add a type for RollupOptionsWithOutput

refactor/types: add a TSDXConfig type

another PR by a contributor exposes the types for tsdx.config.js in order to be used in JSDoc, so this makes it so only a single type is needed and exported

Review Notes

The passPerPreset augmentation for @rollup/plugin-babel / @types/babel__core that is mentioned above is pretty confusing. I decided to leave it as is for now so as to potentially change anything, but my logs seem to show it isn't used 😕 🤔 :

Babel log output:

```ts PartialConfig { options: { sourceMaps: true, caller: { name: '@rollup/plugin-babel', supportsStaticESM: true, supportsDynamicImport: true, supportsTopLevelAwait: true }, filename: '[redacted]/tsdx/stage-build-default/src/syntax/jsx-import/JSX-B.jsx', babelrc: false, configFile: false, passPerPreset: false, envName: 'test', cwd: '[redacted]/tsdx/stage-build-default', root: '[redacted]/tsdx/stage-build-default', plugins: [], presets: [] }, babelignore: undefined, babelrc: undefined, config: undefined } { sourceMaps: true, caller: { name: '@rollup/plugin-babel', supportsStaticESM: true, supportsDynamicImport: true, supportsTopLevelAwait: true }, filename: '[redacted]/tsdx/stage-build-default/src/syntax/jsx-import/JSX-B.jsx', babelrc: false, configFile: false, passPerPreset: false, envName: 'test', cwd: '[redacted]/tsdx/stage-build-default', root: '[redacted]/tsdx/stage-build-default', plugins: [ ConfigItem { value: [Function], options: {}, dirname: '[redacted]/tsdx/stage-build-default', name: undefined, file: [Object] }, ConfigItem { value: [Function: _default], options: {}, dirname: '[redacted]/tsdx/stage-build-default', name: undefined, file: [Object] }, ConfigItem { value: [Function], options: {}, dirname: '[redacted]/tsdx/stage-build-default', name: undefined, file: [Object] }, ConfigItem { value: [Function], options: [Object], dirname: '[redacted]/tsdx/stage-build-default', name: undefined, file: [Object] }, ConfigItem { value: [Function], options: [Object], dirname: '[redacted]/tsdx/stage-build-default', name: undefined, file: [Object] } ], presets: [ ConfigItem { value: [Function], options: [Object], dirname: '[redacted]/tsdx/stage-build-default', name: undefined, file: [Object] } ] } PartialConfig { options: { sourceMaps: true, caller: { name: '@rollup/plugin-babel', supportsStaticESM: true, supportsDynamicImport: true, supportsTopLevelAwait: true }, filename: '[redacted]/tsdx/stage-build-default/src/syntax/jsx-import/JSX-B.jsx', babelrc: false, configFile: false, passPerPreset: false, envName: 'test', cwd: '[redacted]/tsdx/stage-build-default', root: '[redacted]/tsdx/stage-build-default', plugins: [], presets: [] }, babelignore: undefined, babelrc: undefined, config: undefined } ```

Misc

This will be rebased in as each commit is independent and some have some lengthy messages.

jaredpalmer / tsdx