[VETS-API] Bump rack gem 2.2.9 -> 3.1.4

[ryan-mcneil]

Issue Description

Rack is due for a significant update, including a major version bump. There's a Dependabot PR with a TON of broken specs. This might need some thoughtful attention

Requirements to update rack to 3.1.4 (in vets-api):

• httpi 4+
• savon 2.15.1 (ticket to bump and re-record cassettes here)
• bgs-ext (bump req'd) - ticket here
  • savon 2.14.0 -> 2.15.1
  • ruby 3+
• connect_vbms (Steven completed - tag: v2.1.0, PR)
  • httpi 2.5 -> 4+

NOTES:

• Removing utf8-cleaner gem cleans up ~120 failing tests, but should probably replaced with something with comparable functionality, as described in #93388

---

Tasks

• [ ] Fix issues in dependabot PR and bump rack

Acceptance Criteria

• [ ] rack is bumped and merged to prod

[ryan-mcneil]

Duplicates #74448, but we'll use this one

[ryan-mcneil]

TL;DR - We want to update to Rack 3+, which requires httpi 4+, but two of our gems (bgs_ext and connect_vbms) are holding it back.

I started investigating, and realized that at least one of the errors is due to a constant that was removed in rack 3 is being used in our current version of httpi (2.5), which is held back by savon 12.1 which is in turn held back by us having so far been able to bump to the latest bgs_ext release which would get us to savon 14.0 and httpi >= 2.4.5. UPDATE: httpi is ALSO held back by connect_vbms. I'll talk to Steven about bumping the dependency in his fork.

The following errors are because of httpi/savon:

• uninitialized constant Rack::Utils::HeaderHash

We'll block this for now, as it doesn't make much sense to explore the 300+ errors if a lot of them could be caused by the same thing

[ryan-mcneil]

The following ticket clears up ~120 of the ~400 failing tests: #93388