Fix "matches" handling of non-string types

[wigbam]

This should fix handling of non-string fields when using matches. See amended test for example. Before the fix matches would fail on non-string fields with the following error:

=== RUN   TestStub/find_nested_stub_matches_regex_map
    --- FAIL: TestStub/find_nested_stub_matches_regex_map (0.00s)
panic: interface conversion: interface {} is float64, not string [recovered]
	panic: interface conversion: interface {} is float64, not string

goroutine 34 [running]:
testing.tRunner.func1.2({0x11cb960, 0xc00013ddd0})
	/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1209 +0x24e
testing.tRunner.func1()
	/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1212 +0x218
panic({0x11cb960, 0xc00013ddd0})
	/usr/local/Cellar/go/1.17/libexec/src/runtime/panic.go:1038 +0x215
github.com/tokopedia/gripmock/stub.regexMatch({0x11bdb60, 0xc0000a7a80}, {0x11bdb60, 0xc0000a7b58})
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/storage.go:174 +0x167
github.com/tokopedia/gripmock/stub.find({0x11bdb60, 0xc0000a7a80}, {0x11bdb60, 0xc0000a7b58}, 0x68, 0x0, 0x12105e0)
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/storage.go:261 +0x1de
github.com/tokopedia/gripmock/stub.find({0x11c96c0, 0xc00013da10}, {0x11c96c0, 0xc00013dce0}, 0x1, 0x0, 0x12105e0)
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/storage.go:255 +0x265
github.com/tokopedia/gripmock/stub.find({0x11c96c0, 0xc00013d9e0}, {0x11c96c0, 0xc00013dcb0}, 0x1, 0x0, 0x12105e0)
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/storage.go:255 +0x265
github.com/tokopedia/gripmock/stub.find({0x11c96c0, 0xc00013d9b0}, {0x11c96c0, 0xc00013dc80}, 0x1, 0x0, 0x12105e0)
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/storage.go:255 +0x265
github.com/tokopedia/gripmock/stub.matches(...)
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/storage.go:193
github.com/tokopedia/gripmock/stub.findStub(0xc00013dc20)
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/storage.go:89 +0x813
github.com/tokopedia/gripmock/stub.handleFindStub({0x1245050, 0xc0000ed200}, 0xc000128e00)
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/stub.go:151 +0x10e
github.com/tokopedia/gripmock/stub.TestStub.func18(0x0)
	/Users/wigbam/workspace/intellij/opensource/gripmock/stub/stub_test.go:358 +0xdb
testing.tRunner(0xc000164000, 0xc00014a9a0)
	/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1259 +0x102
created by testing.(*T).Run
	/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1306 +0x35a

This is my first ever attempt at Golang, so amend as you see fit 😄

[mgerasimchuk]

@jekiapp please look at this))

Also faced with this problem((

[sejin-P]

Suggested change

	var expectedStr, expectedStringOk = expect.(string)
	var actualStr, actualStringOk = actual.(string)
	expectedStr, expectedStringOk := expect.(string)
	actualStr, actualStringOk = actual.(string)