Mattermost-server: Convert tests in model/search_params_test.go into table testing

[mattermod]

Convert tests in model/searchparamstest.go into table testing.

As an example you can use the already existing table testing tests in the
same file. If you need to know more about table testing, you can take a look
to the following document https://github.com/golang/go/wiki/TableDrivenTests.

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JIRA: https://mattermost.atlassian.net/browse/MM-23192

[tomasmik]

Let's go. I'm ready!

[jespino]

@tomasmik Awesome! thanks! :tada:

[fedealconada]

Are you working on this @tomasmik ?

[tomasmik]

Are you working on this @tomasmik ?

Yes, half way done.