Remove `ExtensionFileSourceCode::LoadedFromFsDuringSnapshot` and feature
`include_js_for_snapshotting` since they leak paths that are only
applicable in this repo to embedders. Replace with feature
`exclude_js_sources`. Additionally the feature
`force_include_js_sources` allows negating it, if both features are set.
We need both of these because features are additive and there must be a
way of force including sources for snapshot creation while still having
the `exclude_js_sources` feature. `force_include_js_sources` is only set
for build deps, so sources are still excluded from the final binary.
You can also specify `force_include_js_sources` on any extension to
override the above features for that extension. Towards #19398.
But there was still the snapshot-from-snapshot situation where code
could be executed twice, I addressed that by making `mod_evaluate()` and
scripts like `core/01_core.js` behave idempotently. This allowed
unifying `ext::init_ops()` and `ext::init_ops_and_esm()` into
`ext::init()`.
Spend quite some time trying to get this working. With proper example
would have been a lot faster. So this is pr with the example. I also
rearranged examples a little bit to allow for addition of more examples
