fix(x/upgrade): Stop treating inline JSON as a URL (backport #19706)

[mergify]

Description

Closes: #19686

Detect URLs with ParseRequestURI rather than Parse, since the former is limited to absolute URLs while the latter recognizes undesirable input such as {}.

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Author Checklist

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• added a changelog entry to CHANGELOG.md
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Summary by CodeRabbit

• Bug Fixes
  • Fixed an issue where inline JSON was not correctly treated as a URL during parsing.
  • Added a new test case to ensure empty JSON objects are parsed correctly without errors.

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This is an automatic backport of pull request #19706 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 5a733e8 has failed:

On branch mergify/bp/release/v0.50.x/pr-19706
Your branch is up to date with 'origin/release/v0.50.x'.

You are currently cherry-picking commit 5a733e81d.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   x/upgrade/plan/info.go
	modified:   x/upgrade/plan/info_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   x/upgrade/CHANGELOG.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[julienrbrt]

note to myself, next release run, test and tag v0.1.2