bug #18224 [PropertyAccess] Remove most ref mismatches to improve perf (nicolas-grekas)

This PR was merged into the 2.3 branch.

Discussion
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[PropertyAccess] Remove most ref mismatches to improve perf

| Q             | A
| ------------- | ---
| Branch?       | 2.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This PR is for PHP5 where ref mismatches is a perf pain: it removes all ref mismatches along the "getValue" path, and keeps only the required ones on the "setValue" path.

Commits
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72940d7 [PropertyAccess] Remove most ref mismatches to improve perf

Author: fabpot