refactor: parts of hottier

[de-sh]

Fixes #XXXX.

Description

• Uses FuturesUnordered to manage async tasks
• Reuses get_stream_path_for_date where possible
• Refactors human_size parsing
• Streams through results instead of collecting
• Stores sizes as integers in memory

---

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 12995883515

Details

• 34 of 264 (12.88%) changed or added relevant lines in 6 files are covered.
• 11 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.2%) to 12.919%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/metadata.rs	0	1	0.0%
src/storage/mod.rs	0	1	0.0%
src/validator.rs	0	8	0.0%
src/utils/human_size.rs	34	63	53.97%
src/handlers/http/logstream.rs	0	38	0.0%
src/hottier.rs	0	153	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/migration/mod.rs	1	0.0%
src/validator.rs	1	0.0%
src/handlers/http/logstream.rs	2	1.73%
src/hottier.rs	7	0.0%

Totals
Change from base Build 12991591562:	0.2%
Covered Lines:	2477
Relevant Lines:	19174

---

💛 - Coveralls

[nikhilsinhaparseable]

@de-sh there is a change in behaviour of the PUT /hottier API
request body expected -
before change: {"size":"10737418240"}
after change: {"size":"10 GiB"}

even the GET /hottier API is failing with error -
Serde(Error("Could not parse given size", line: 1, column: 42))

can you please verify that there should be no behavioural change in the existing APIs.

[nikhilsinhaparseable]

looks good