Fixes #18979.
This changes the predicate for allowing `ext:` specifier resolution from
`snapshot_loaded_and_not_snapshotting` to `ext_resolution_allowed` which
is only set to true during the extension module loading phase. Module
loaders as used in core
are now declared as `ExtModuleLoader` rather than `dyn ModuleLoader`.
This commit moves Deno JS runtime, ops, permissions and
inspector implementation to new "deno_runtime" crate located
in "runtime/" directory.
Details in "runtime/README.md".
Co-authored-by: Ryan Dahl <ry@tinyclouds.org>