[HttpFoundation][NamespacedAttributeBag] Refactoring of resolveKey() method
merged branch alexpods/patch-3 (PR #8003)

This PR was merged into the master branch.

Discussion
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[HttpFoundation][NamespacedAttributeBag] Refactoring of resolveKey() method

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Just code enhancement. Low priority.

1) We don't need to call strlen($name) as last argument of substr() function
2) We don't need to call strrpos (or strpos) two times.

Commits
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a644516 [HttpFoundation][NamespacedAttributeBag] Refactoring of resolveKey() method