test: use `T.TempDir` to create temporary test directory

[Juneezee]

A testing cleanup.

This pull request replaces ioutil.TempDir with t.TempDir. We can use the T.TempDir function from the testing package to create temporary directory. The directory created by T.TempDir is automatically removed when the test and all its subtests complete.

This saves us at least 2 lines (error check, and cleanup) on every instance, or in some cases adds cleanup that we forgot.

Reference: https://pkg.go.dev/testing#T.TempDir

func TestFoo(t *testing.T) {
	// before
	tmpDir, err := ioutil.TempDir("", "")
	assert.NoError(t, err)
	defer os.RemoveAll(tmpDir)

	// now
	tmpDir := t.TempDir()
}

[roseduan]

Can you test it in Windows environment? In windows we maybe encounter some problems when we delete the files.

[Juneezee]

Marking this PR as draft first before https://github.com/flower-corp/lotusdb/pull/46 is merged.

[Juneezee]

Hi @roseduan, please take a look at this PR as well after merging #46 . I'll rebase once #46 has been merged. Thank you.

[Juneezee]

Hi @roseduan, it's been a while since this PR was last reviewed. Would you mind taking a few minutes again and possibly merge it? Thanks in advance

[Juneezee]

friendly ping @roseduan

[roseduan]

I will rebuild the whole project and do more changes, please follow me the V2 version. Thanks for your support!