Fetching ohttp-keys should time out quickly

[zealsham]

This pr adds a timeout time of 10 seconds when trying to connect to a relay and the response time is longer than normal . addresses #968

Pull Request Checklist

Please confirm the following before requesting review:

• A human has reviewed every single line of this code before opening the PR (no auto-generated, unreviewed LLM/robot submissions).
• I have read CONTRIBUTING.md and rebased my branch to produce hygienic commits.

[coveralls]

Pull Request Test Coverage Report for Build 17278728526

Details

• 6 of 12 (50.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.04%) to 85.676%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
payjoin/src/core/io.rs	6	12	50.0%

Totals
Change from base Build 17278137158:	-0.04%
Covered Lines:	7973
Relevant Lines:	9306

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💛 - Coveralls

[DanGould]

Primo. Nice and easy.

utACK 034e89d

Have you smoke tested this at all to iterate through bad relays? I wonder how the experience is vs 5 seconds.

[DanGould]

This has me wondering also, since fetching can happen multiple times, if the client should later be cached or re-used so that it can get a performance edge or if that only makes sense for custom clients and not the one we ship with io

[spacebear21]

Tangential to this issue, I also wonder if implementers could parallelize requests to multiple ohttp relays instead of trying them sequentially, and process whatever response returns first.

[DanGould]

It'd be nice to be able to test this experience, ESPECIALLY IN MOBILE! but I'll merge this for now. I'll open an "audit network disruption experience" issue.