test: followups & integration tests optimizations

[juan518munoz]

Addressed remaining comments from #2481:

• Removed into_client_builder Test: code simplifications #2481 (comment)
• Switched to ECDSA auth scheme, kept test_onchain_notes_flow with RPO Test: code simplifications #2481 (comment)
• Removed overly complex assertion Test: code simplifications #2481 (comment)
• AccountSetup is now able to take a pre-built Account Test: code simplifications #2481 (comment)

Optimization attemps:

• The Funder no longer waits for its payment to commit before returning the funding note. That wait was moved to a flush() call after the test body, so a funded account can build its own transaction as soon as the node accepts the payment. Each test process now claims one funder wallet for its whole life instead of claiming one per payment.
• Increased test thread count from 3 to 6, under the assumption that most test time is under proving reverted in 244152c

New job to meassure test speedup/slowdown:

• Added a new job that prints a table on every PR comparing its (tests) CI times against the dest branch

[github-actions]

CI test timings

Test type	next	This PR	% diff
Unit tests	19m 57s	15m 35s	-21.9%
Integration tests	40m 27s	34m 19s	-15.2%
AggLayer tests	10m 09s	9m 55s	-2.3%
miden-bench smoke tests	5m 51s	5m 31s	-5.7%
Total	76m 24s	65m 20s	-14.5%

Base run: 5f6869a of 2026-09-10 on next. This run: 244152c.
Job wall-clock time, queue time excluded. The total adds up only the rows that ran on both sides.

[juan518munoz]

Should we mark this as no-changelog? Considering it's not user facing

[igamigo]

LGTM!