Add function dateTimeToUUIDv7

[samradovich]

Resolves: #84244

Changelog category (leave one):

• New Feature

Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):

Added function dateTimeToUUIDv7 to convert a DateTime value to a UUIDv7. Example usage: SELECT dateTimeToUUIDv7(toDateTime('2025-08-15 18:57:56')) returns 0198af18-8320-7a7d-abd3-358db23b9d5c.

[CLAassistant]

All committers have signed the CLA.

[samradovich]

@rschu1ze Please feel free to add a WIP label or something similar.

You will notice that this is nearly identical to the generateUUIDv7 function... It would likely be better to merge shared functionality into a single file. I am happy to refactor things if you agree but, for now, this felt like an easy way to get the idea out there. Since the changes are purely additive we can review the function in isolation.

I will be back in the office on Sunday 7/27 so I won't be able to reliably respond to comments until then. Thanks for the review in advance!

[clickhouse-gh]

Workflow [PR], commit [2467157]

Summary: ❌

job_name	test_name	status	info	comment
Stateless tests (amd_debug, AsyncInsert, s3 storage, parallel)		failure
	02443_detach_attach_partition	FAIL
Stateless tests (amd_msan, parallel, 1/2)		failure
	02950_parallel_replicas_used_count	FAIL
	03581_parallel_replicas_read_empty_ranges	FAIL

[rschu1ze]

Stateless tests (amd_debug, AsyncInsert, s3 storage, parallel)

• 02443_detach_attach_partition 02443_detach_attach_partition is flaky  #54748