[Spanify] span size/offset to conform to size_t

[cdesouza-chromium]

There's some tightening around values passed into span, with StrictNumeric<size_t> being enforced. This is mostly unimportant when dealing with compile-time values, as they can be validated on the spot, however it does affect several places where the value is only known at runtime, and a signed value was being used.

Chromium changes:
https://chromium.googlesource.com/chromium/src/+/4937ad9ae64d9d3f05d13c9d041769432a12281b

commit 4937ad9ae64d9d3f05d13c9d041769432a12281b
Author: Peter Kasting <[email protected]>
Date:   Tue Nov 26 22:58:16 2024 +0000

    Use StrictNumeric<size_t> for more span methods.

    Changes subspan(), split_at(), at(), and get_at() to match pre-existing
    usage in constructors, first(), last(), etc.

    Bug: 364987728

Resolves brave/brave-browser#42627

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
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  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, 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
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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/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[supermassive]

wallet core lgtm

[brave-builds]

Released in v1.75.71