Add __ParamCoerceModeFalse to various ext file functions

Summary: After the ext file HNI conversion, the return value of various file functions have been changed from false to NULL. Setting these functions' param coerce mode to false would fix the issue.

Reviewed By: @JoelMarcey

Differential Revision: D1700631
Fix Arr=Packed | BoxedInitCell.

Summary: We weren't correctly dropping the specialization, and hitting an assert when
constructing the new type.

Reviewed By: @jdelong

Differential Revision: D1721056
Make timeout flag sticky

Summary: Occasionally we see long-lived requests that fail to timeout.  What
probably happens is that the TimeoutException is generated, the timeout
surprise flag is unset, and then the exception is caught by some block that
simply drops it.  While we could keep auditing catch blocks, it seems more
reliable to simply make timeouts sticky, so that we'll re-raise the exception
at the next opportunity.

Reviewed By: @jdelong

Differential Revision: D1711487