Extensions allow declarative extensions to "JsRuntime" (ops, state, JS or middleware).
This allows for:
- `op_crates` to be plug-and-play & self-contained, reducing complexity leaked to consumers
- op middleware (like metrics_op) to be opt-in and for new middleware (unstable, tracing,...)
- `MainWorker` and `WebWorker` to be composable, allowing users to extend workers with their ops whilst benefiting from the other infrastructure (inspector, etc...)
In short extensions improve deno's modularity, reducing complexity and leaky abstractions for embedders and the internal codebase.
This commit adds blob URL support. Blob URLs are stored in a process
global storage, that can be accessed from all workers, and the module
loader. Blob URLs can be created using `URL.createObjectURL` and revoked
using `URL.revokeObjectURL`.
This commit does not add support for `fetch`ing blob URLs. This will be
added in a follow up commit.
