This commit adds new option to "Worker" Web API that allows to
configure permissions.
New "Worker.deno.permissions" option can be used to define limited
permissions to the worker thread by either:
- inherit set of parent thread permissions
- use limited subset of parent thread permissions
- revoke all permissions (full sandbox)
In order to achieve this functionality "CliModuleLoader"
was modified to accept "initial permissions", which are used
for top module loading (ie. uses parent thread permission set
to load top level module of a worker).
This PR hot-fixes permission escapes in dynamic imports, workers
and runtime compiler APIs.
"permissions" parameter was added to public APIs of SourceFileFetcher
and appropriate permission checks are performed during loading of
local and remote files.
