Add opportunity to trigger setup/teardown for subtest

[qerdcv]

Summary

Add opportunity to setup or teardown each subtest

Changes

• Added method to the Suite struct that allows to save parent suite (with it's methods) and execute it in future
• Added SetupSubTest interface that allows to execute function before each subtest
• Added TearDownSubTest interface that allows to execute function after each subtest is done

Motivation

I find very useful to have opportunity to setup/tear down subtest, and I decide to try add it.

Example usage

type MySuite struct {
    suite.Suite
    db *sql.DB
} 

func (ms *MySuite) SetupSuite() {
   // abstract code
   // setup database in test container and save it into the ms.db
}

func (ms *MySuite) TearDownSubTest() {
    // abstract code
    // after each subtest run I need to cleanup db
    // to avoid conflicts in my tests and make tests more isolated from each other
}

Related issues

Closes: #1031
Closes: #832

[RostislavBlatman]

very important feature for table-tests. Lets merge it

[qerdcv]

Hi! Can somebody check it?
@glesica @boyan-soubachov @mvdkleijn

[boyan-soubachov]

LGTM. Thank you for your contribution :)

[qerdcv]

When will the next release be? :)
The last one was about year ago

[FalcoSuessgott]

Also would love a new release for this feature:)

[AlessandroBagnoli]

ehy, any news on when this will be released? :)

[rcaetanomeli]

Also waiting for the release o/

[boyan-soubachov]

ehy, any news on when this will be released? :)

Just released in v1.8.2