chore: remove cost voting r2 - full functional removal (post-4.0)

[cylewitruk-stacks]

⚠️ DO NOT MERGE - This is a draft PR for review only and this branch will be retargeted to develop once pox-wf-integration merges for the final removal.
ℹ️ Currently targets pox-wf-integration but is based on chore/remove-cost-voting-r1 and thus includes its diff.

This PR fully removes the SIP-006's .cost-voting contract's functional side-effects, as proposed in SIP-044, and is contingent on SIP-044's acceptance and activation in epoch 4.0, together with the r1 precursor (#7341).

Description

Applicable issues

• Part 2 of https://github.com/stx-labs/core-epics/issues/255 (subtask https://github.com/stx-labs/core-epics/issues/363)

Additional info (benefits, drawbacks, caveats)

• Removes a whole bunch of unused code/tests.
• The removal of is_cost_contract_eligible from ContractAnalysis is backwards-compatible as serde_json ignores unknown fields during deserialization of previously stored analyses.

Checklist

• Test coverage for new or modified code paths
• For new Clarity features or consensus changes, add property tests (see docs/property-testing.md)
• Changelog fragment(s) or "no changelog" label added (see changelog.d/README.md)

[Copilot]

Pull request overview

This draft PR completes the “r2” cleanup for SIP-044 by removing the remaining functional machinery and test coverage for .cost-voting-driven runtime cost updates, leaving the VM to always resolve runtime costs via the epoch’s default boot cost contract (costs, costs-2, costs-3, costs-4, costs-5). It also refactors test utilities around epoch ranges and boot-contract initialization (notably for epoch 4.0’s costs-5 setup).

Changes:

• Remove cost-voting integration paths in Clarity cost tracking (including contract-call cost “short-circuiting”), plus associated analysis hooks and tests.
• Add a test-only StacksEpochRangeTestExt to express epoch ranges via standard Rust range syntax and update affected tests.
• Refactor epoch 4.0 boot contract instantiation to allow initializing costs-5 without requiring full epoch 4.0 boot (PoX-5 / sBTC stubs), and update costs tests accordingly.

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
stackslib/src/net/api/tests/postblock_v3.rs	Removes an unused hash/Merkle import after related functionality/test coverage removal.
stackslib/src/clarity_vm/tests/costs.rs	Refactors costs test setup to bootstrap only needed epochs/contracts and removes cost-voting integration tests.
stackslib/src/clarity_vm/clarity.rs	Adds reusable boot-contract tx helpers and a dedicated epoch 4.0 costs-5 instantiation path used by tests and epoch init.
stackslib/src/chainstate/tests/runtime_tests.rs	Migrates epoch range construction to range-based test extension helpers.
stackslib/src/chainstate/tests/runtime_analysis_tests.rs	Migrates epoch range construction to range-based test extension helpers.
stackslib/src/chainstate/tests/consensus.rs	Replaces StacksEpochId::since usage with range-based iteration and updates associated docs.
stackslib/src/chainstate/tests/consensus_unit_tests.rs	Migrates deploy epoch lists to the new range-based helper.
stackslib/src/chainstate/stacks/boot/contract_tests.rs	Removes .cost-voting contract tests and arithmetic-only checks tied to cost-voting eligibility.
stacks-node/src/tests/neon_integrations.rs	Removes the ignored end-to-end cost-voting integration test.
stacks-common/src/types/mod.rs	Removes test-only since/between helpers and adds StacksEpochRangeTestExt + additional test-only epoch helpers.
stacks-common/src/types/tests.rs	Adds unit tests validating StacksEpochRangeTestExt range behavior and edge cases.
clarity/src/vm/tests/epoch_gating.rs	Updates monotonicity test to use range-based epoch slice helper.
clarity/src/vm/functions/database.rs	Removes contract-call cost short-circuiting path and always executes contract calls normally.
clarity/src/vm/costs/mod.rs	Removes cost-voting state loading/applying and associated circuit tracking; always loads default boot cost contract for the current epoch.
clarity/src/vm/contexts.rs	Removes run_free and short_circuit_contract_call plumbing from execution/global contexts.
clarity/src/vm/ast/mod.rs	Updates test cost tracker implementation to match the simplified CostTracker trait.
clarity/src/vm/analysis/types.rs	Removes is_cost_contract_eligible from ContractAnalysis.
clarity/src/vm/analysis/type_checker/v2_1/mod.rs	Updates CostTracker implementation after removing short-circuit API.
clarity/src/vm/analysis/type_checker/v2_05/mod.rs	Updates imports/CostTracker implementation after removing short-circuit API.
clarity/src/vm/analysis/mod.rs	Removes arithmetic-checker pass wiring from analysis pipeline.
clarity/src/vm/analysis/contract_interface_builder/mod.rs	Removes destructuring of the deleted is_cost_contract_eligible field.
clarity/src/vm/analysis/arithmetic_checker/tests.rs	Deletes arithmetic-checker tests tied to cost-voting eligibility.
clarity/src/vm/analysis/arithmetic_checker/mod.rs	Deletes the arithmetic-checker pass previously used for cost-voting contract eligibility.
changelog.d/7341-cost-voting-epoch-4-0-gate	Adds/updates a changelog fragment (currently describing only the r1 gating).

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