rpc: replace `hyper::Client` with `reqwest::Client`

[mzabaluev]

Closes #1342

In hyper, the high-level Client implementation is going to be removed in the next major release. The current client lacks built-in support for HTTP proxies, and we want to ditch hyper-proxy as it is unmaintained and its webpki dependency has a known security issue.

• [x] Referenced an issue explaining the need for the change
• [ ] Updated all relevant documentation in docs
• [ ] Updated all code comments where relevant
• [ ] Wrote tests
• [x] Added entry in .changelog/

[codecov-commenter]

Codecov Report

Merging #1362 (c5f186d) into main (89da5f6) will decrease coverage by 0.6%. The diff coverage is 62.2%.

:exclamation: Current head c5f186d differs from pull request most recent head 7f9b850. Consider uploading reports for the commit 7f9b850 to get more accurate results

@@           Coverage Diff           @@
##            main   #1362     +/-   ##
=======================================
- Coverage   60.7%   60.2%   -0.6%     
=======================================
  Files        274     274             
  Lines      26864   27199    +335     
=======================================
+ Hits       16322   16386     +64     
- Misses     10542   10813    +271     

Files	Coverage Δ
rpc/src/client/transport/auth.rs	100.0% <100.0%> (ø)
rpc/src/error.rs	95.2% <100.0%> (-0.1%)	:arrow_down:
rpc/src/rpc_url.rs	66.6% <76.0%> (ø)
rpc/src/client/transport/websocket.rs	63.9% <15.3%> (-0.4%)	:arrow_down:
rpc/src/client/transport/http.rs	34.5% <60.3%> (+14.4%)	:arrow_up:

... and 5 files with indirect coverage changes

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[romac]

Love all that deleted code 🥇