refactor: simply store StreamType

[de-sh]

Fixes #XXXX.

Description

No functional changes, just saves on cost of conversion into String

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How to test

1. Start a parseable instance without this change.
2. Create a stream, push data onto it.
3. Shutdown parseable, update binary with this change.
4. Restart parseable with same config as before, ensure internal streams are considered as such and no conflicts in working.

This PR has:

• been tested to ensure log ingestion and log query works.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.

[coveralls]

Pull Request Test Coverage Report for Build 13025754244

Details

• 0 of 21 (0.0%) changed or added relevant lines in 6 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.002%) to 12.949%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/handlers/http/modal/utils/logstream_utils.rs	0	1	0.0%
src/storage/mod.rs	0	1	0.0%
src/storage/object_storage.rs	0	1	0.0%
src/handlers/http/modal/query/querier_logstream.rs	0	3	0.0%
src/metadata.rs	0	7	0.0%
src/handlers/http/logstream.rs	0	8	0.0%

Totals
Change from base Build 13025432081:	-0.002%
Covered Lines:	2477
Relevant Lines:	19129

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💛 - Coveralls

[nikhilsinhaparseable]

looks good