This PR introduces two type alias to avoid the confusing const generic `pub struct Codegen<'a, const MINIFY: bool>`
* CodeGenerator - Code generator without whitespace removal.
* WhitespaceRemover - Code generator with whitespace removal.
Usage is changed to a builder pattern:
```rust
CodeGenerator::new()
.enable_comment(...)
.enable_sourcemap(...)
.build(&program);
```
The sourcemap implement port from
[rust-sourcemap](https://github.com/getsentry/rust-sourcemap), but has
some different with it.
- Encode sourcemap at parallel, including quote `sourceContent` and
encode token to `vlq` mappings.
- Avoid `Sourcemap` some methods overhead, like `SourceMap::tokens()`
caused extra overhead at common cases. Here using `SourceViewToken` to
instead of it.
