Sign Solana transaction based on selected account instead of fee payer

[yrliou]

Resolves brave/brave-browser#27051

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally: npm run test -- brave_browser_tests, npm run test -- brave_unit_tests, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

The specific use case has been covered by new browser/unit tests.
For manual testing, please try Sign and Send Transaction in https://pwgoom.csb.app/ for a basic regression test with both software and hardware account(ledger).

[darkdh]

++

[srirambv]

Verification passed on

Brave	1.48.23 Chromium: 108.0.5359.71 (Official Build) nightly (64-bit)
Revision	1e0e3868ee06e91ad636a874420e3ca3ae3756ac-refs/branch-heads/5359@{#1016}
OS	Windows 11 Version 22H2 (Build 22623.1020)

• Verified steps from PR
• Verified able to submit a Sign and Send transaction
• Verified able to submit and confirm transaction on both software and hardware wallet

16154.mov

---

Verification passed on Oppo Reno 5 with Android 12 running 1.48.23 x64 Nightly build

• Verified able to submit a sign and send transaction

16154-ARM.mp4