Remove hyper and migrate to axum.

[zealsham]

This pr is part of the process of transitioning to axum from hyper . Hyper is quite low level and that type of low level details isn't needed for our use case .

Pull Request Checklist

Please confirm the following before requesting review:

• I have disclosed my use of
  AI
  in the body of this PR.
• I have read CONTRIBUTING.md and rebased my branch to produce hygienic commits.

[coveralls]

Pull Request Test Coverage Report for Build 17893736401

Details

• 160 of 222 (72.07%) changed or added relevant lines in 3 files are covered.
• 5 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.2%) to 84.924%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
payjoin-directory/src/main.rs	0	1	0.0%
payjoin-directory/src/lib.rs	159	220	72.27%

Files with Coverage Reduction	New Missed Lines	%
payjoin-directory/src/lib.rs	5	57.53%

Totals
Change from base Build 17883934451:	0.2%
Covered Lines:	8500
Relevant Lines:	10009

---

💛 - Coveralls

[zealsham]

#1026 just went in , so this requires a rebase , will do that