Update FileLoader to fix issue #10339

FileLoader now uses resolved FileLoader's (the one that explicitly
supports that resource) FileLocatorInterface instance before falling
back to its own when trying to load resources in import() method.
bug #10348 Update FileLoader to fix issue #10339 (msumme)

This PR was merged into the 2.3 branch.

Discussion
----------

Update FileLoader to fix issue #10339

This fixes an issue in Symfony\Component\Config\Loader\FileLoader

| Q             | A
| ------------- | ---
| Bug fix?      |  yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |  #10339
| License       | MIT
| Doc PR        |  none

Commits
-------

3988728 Update FileLoader to fix issue #10339
added a BC comment
fixed Kernel::stripComments() normalizing new-lines

This makes normalizing new-lines less error-prone
when a string contains multiple new line-lines
bug #10351 [HttpKernel] fix stripComments() normalizing new-lines (sstok)

This PR was merged into the 2.3 branch.

Discussion
----------

[HttpKernel] fix stripComments() normalizing new-lines

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10227
| License       | MIT
| Doc PR        |

This makes normalizing new-lines less error-prone
when a string contains multiple new line-lines

Commits
-------

63032c7 fixed Kernel::stripComments() normalizing new-lines
changed some PHPUnit assertions to more specific ones
minor #10358 PHPUnit more specific assertions (fabpot)

This PR was merged into the 2.3 branch.

Discussion
----------

PHPUnit more specific assertions

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10357
| License       | MIT
| Doc PR        | n/a

Commits
-------

4927d0c changed some PHPUnit assertions to more specific ones