ci: fix remaining master CI failures

[decofe]

Summary

• keep sccache enabled in CI MPP, but remove Swatinem/rust-cache from that workflow because the action itself fails before build/test starts
• extend the slow nextest override to cover the remaining slow CI tests seen on master: chisel live logs and wallet session wrapper
• update slow nextest filters to match module-qualified names such as cmd::clone::tests::test_clone_*, bind::..., cmd::can_bind_e2e, and script::...
• make the wallet session project-root assertion tolerate Windows-rendered temp paths while still checking root forwarding
• fix the Tempo dependency bump workflow to create PRs against master, not main

Why

• master already includes ci: increase timeouts for slow CLI integration tests #15117, but the latest master CI still failed on additional timeout-prone tests, a Windows-only rendered path assertion, and CI MPP rust-cache setup
• the previous timeout filters were anchored to bare test names, but nextest reports these tests with module-qualified names, so the override did not apply and tests still timed out at the default 90s
• the PR run showed CI MPP still failing inside Swatinem/rust-cache even with save-if: false, so CI MPP now relies on sccache only
• the scheduled Tempo dependency bump job successfully pushed its branch, then failed PR creation because this repo's base branch is master

Validation

• git diff --check
• cargo metadata --no-deps --format-version 1
• rustfmt crates/script/src/wallet_session.rs --edition 2024 --check
• parsed .config/nextest.toml with Python tomllib
• regex sanity check matched latest failed/flaky nextest names, including cmd::clone::tests::test_clone_*, bind tests, can_bind_e2e, script concurrency, chisel live logs, wallet session, and vaddr_e2e::...

Note: targeted cargo tests were started but stopped during cold dependency compilation before test execution.

Prompted by: @grandizzy