Added reloading of fallback catalogues when calling addResource() (#7715)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7715
| License       | MIT
| Doc PR        |
Reset all catalogues when adding resource to fallback locale (#7715, #7819)

Slightly refactored testAddResourceAfterTrans()
and replaced costly part with reset all catalogues

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7715, #7819
| License       | MIT
| Doc PR        |
merged branch hilobok/ticket_7715 (PR #7819)

This PR was submitted for the master branch but it was merged into the 2.2 branch instead (closes #7819).

Discussion
----------

[Translator] Added reloading of fallback catalogues when calling addResource() (#7715)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7715
| License       | MIT
| Doc PR        |

Commits
-------

4f0b063 [Translator] Reset all catalogues when adding resource to fallback locale (#7715, #7819)
5544f36 [Translator] Added reloading of fallback catalogues when calling addResource() (#7715)