Previously, when we needed to detect whether a file is external to a
package, we only checked whether the relative path to the file from the
package's root started with `..`. This would detect external imports
when the packages were siblings (e.g. peer dependencies or hoisted to
the top of `node_modules/` by the package manager), but would fail to
detect imports from packages located in nested `node_modules/` as
external. For example, importing `node_modules/foo/node_modules/bar`
from a file in `node_modules/foo/` would be considered internal to the
`foo` package.
This could result in processing/analyzing more files than necessary.
More importantly it could lead to errors due to trying to analyze
non-Angular packages that were direct dependencies of Angular packages.
This commit fixes it by also verifying that the relative path to a file
does not start with `node_modules/`.
Jira issue: [FW-2068](https://angular-team.atlassian.net/browse/FW-2068)
Fixes#36526
PR Close#36559
6ab43d7335