Prevent MoveBucket from moving a bucket across two different db files

[Elbehery]

This PR adds more test to move bucket feature

• Test moving buckets between two different database files
• Test moving buckets using two different transactions

Refer to #635 (comment)

cc @ahrtr @fuweid

[ahrtr]

Let's add 3 cases below,

• The source tx is readonly, the target tx is readwrite; both are for the same db;
• The source tx is readwrite, and the target tx is readonly; both are for the same db;
• The source bucket and target bucket are not in the same db.

[Elbehery]

Let's add 3 cases below,

• The source tx is readonly, the target tx is readwrite; both are for the same db;
• The source tx is readwrite, and the target tx is readonly; both are for the same db;
• The source bucket and target bucket are not in the same db.

done 👍🏽

[ahrtr]

@Elbehery
Please take a look at the workflow failure, thx

[Elbehery]

@Elbehery Please take a look at the workflow failure, thx

fixed .. my bad, forgot to close the second db file :'(

deep apologies

[Elbehery]

i got it, i used the wrong var to in the defer :'(

[ahrtr]

@Elbehery Please let's try to get this PR merged today before I create the tag 1.4.0-alpha.0

[Elbehery]

@ahrtr updated & rebased 👍🏽

[ahrtr]

minor comment:

Suggested change

	require.Equal(t, expectedErr, mErr)
	require.Equal(t, errors.ErrDifferentDB, mErr)

[ahrtr]

Suggested change

expectedErr := errors.ErrDifferentDB

[Elbehery]

@ahrtr updated

[ahrtr]

lgtm

Thanks