fix(@angular/cli): accept multi-digit array indices in ng config - #34305

PR Checklist

• The commit message follows our guidelines: https://github.com/angular/angular-cli/blob/main/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

parseJsonPath makes bracket segment number only when it is single digit (/^\d$/), so [10] stays string '10' and jsonc-parser cant find it in array
Option help shows a[3].foo.bar[2] as exmaple, nothing says indices stop at 9

Workspace with 12 styles:

ng config projects.app.architect.build.options.styles[9]          # s9.css
ng config projects.app.architect.build.options.styles[10]         # Value cannot be found.
ng config projects.app.architect.build.options.styles[10] x.css   # throws "Can not add index to parent of type array"

What is the new behavior?

Any run of digits is parsed as index, so styles[10] and a[2][13] work for get and set
Quoted segments like a['10'] stay string keys

parseJsonPath is exported now and new cli_spec.ts covers it, multi-digit case fails on main

Does this PR introduce a breaking change?

• Yes
• No

Other information

Unquoted [10] on object now acts like [3] always did, ["10"] still reaches such key