Throw exceptions on empty and not passed parameters, cast `null` to empty string in `SimpleMessageFormatter`

[arogachev]

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	❌
Fixed issues

[what-the-diff[bot]]

• Added test for empty parameter name.
• Fixed bug with empty parameter name in format method (throws exception).
• Changed formatting of parameters to be more consistent and readable:
  • removed spaces around curly braces;
  • added space after comma when there are multiple options for pluralization;
• Removed unnecessary tests from SimpleMessageFormatterTest::formatProvider().

[codecov[bot]]

Codecov Report

Base: 95.30% // Head: 99.62% // Increases project coverage by +4.31% :tada:

Coverage data is based on head (0cd0dd1) compared to base (d87e84d). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #93 +/- ## ============================================ + Coverage 95.30% 99.62% +4.31% - Complexity 105 106 +1 ============================================ Files 13 12 -1 Lines 277 267 -10 ============================================ + Hits 264 266 +2 + Misses 13 1 -12 ``` | [Impacted Files](https://codecov.io/gh/yiisoft/translator/pull/93?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft) | Coverage Δ | | |---|---|---| | [src/SimpleMessageFormatter.php](https://codecov.io/gh/yiisoft/translator/pull/93/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1NpbXBsZU1lc3NhZ2VGb3JtYXR0ZXIucGhw) | `100.00% <100.00%> (+2.38%)` | :arrow_up: | | [src/TranslatorInterface.php](https://codecov.io/gh/yiisoft/translator/pull/93/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RyYW5zbGF0b3JJbnRlcmZhY2UucGhw) | | | | [src/MessageReaderInterface.php](https://codecov.io/gh/yiisoft/translator/pull/93/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL01lc3NhZ2VSZWFkZXJJbnRlcmZhY2UucGhw) | | | | [config/params.php](https://codecov.io/gh/yiisoft/translator/pull/93/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-Y29uZmlnL3BhcmFtcy5waHA=) | `100.00% <0.00%> (ø)` | | | [src/Extractor/ContentParser.php](https://codecov.io/gh/yiisoft/translator/pull/93/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL0V4dHJhY3Rvci9Db250ZW50UGFyc2VyLnBocA==) | `100.00% <0.00%> (+4.54%)` | :arrow_up: | | [src/Translator.php](https://codecov.io/gh/yiisoft/translator/pull/93/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RyYW5zbGF0b3IucGhw) | `100.00% <0.00%> (+7.40%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft)

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