[Feat] LSMTSparseFile support close_seal()

[BigVan]

What this PR does / why we need it:

• close_seal() Method can also convert a LSMTSparseFile as a LSMTReadOnlyFile with 'sparse_rw' tag. Users should be careful to compact such files before uploading them. :D
• And also, a compacted LSMTReadonlyFile shouldn't be committed twice. This PR adds some format check for it.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):

#216

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[liulanzheng]

LGTM