[fs] hailtop.fs makes it impossible to explicitly configure the GCS requester pays project in code

[danking]

What happened?

See: https://hail.zulipchat.com/#narrow/stream/128581-Cloud-support/topic/requester.20pays.20in.20batch

We need a way to configure the RouterFS in a Python file. Maybe hfs.init? I'm not sure.

Version

0.2.120

Relevant log output

No response

[danking]

Where do I write requester pays information?

import hailtop.fs as hfs
with hfs.open('gs://bucket/path/to/file') as fobj:
    ....

[danking]

Probably need an hfs.init?

[danking]

Options:

1. hfs.init. Pros: applies to all uses of open/close/etc. Cons: global state.
2. hfs.open(..., requester_pays_configuration=...). Pros: allows use-site overriding. Cons: user has to specify at every open.
3. both? Pros: easy way to set a default, and allows use-site overrides. Cons: committing ourselves to another global state.

Let's do option (2) for now.