[DependencyInjection] Fix Container::camelize to convert beginning and ending chars

To convert a service ID exactly like Container::get
merged branch GromNaN/dic-camelize (PR #8536)

This PR was merged into the 2.2 branch.

Discussion
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[DependencyInjection] Fix Container::camelize to convert beginning and ending . and _

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7431
| License       | MIT
| Doc PR        | n/a

I'm using strtr to make the conversion in order to ensure that the behavior is the same as `Container::get`.

From the test cases I've added, the following were not passing:

Commits
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485d53a [DependencyInjection] Fix Container::camelize to convert beginning and ending chars