[2.3][HttpFoundation] PDO Session handling enhancements
merged branch MidnightLightning/master (PR #7634)

This PR was squashed before being merged into the master branch (closes #7634).

Discussion
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[2.3][HttpFoundation] PDO Session handling enhancements

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

`PdoSessionHandler` class assumes that the PDO object is set to throw exceptions, not errors. I added a line in the constructor to set that attribute, so configuration/query errors are able to be seen and caught a lot easier.

Commits
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ce8a441 [2.3][HttpFoundation] PDO Session handling enhancements