overlay-only loadgen mode updates: checkValid cleanup and new tx profiles

[marta-lokhova]

No description provided.

[Copilot]

Pull request overview

This PR updates Stellar Core’s overlay-only load generator behavior to run deeper end-to-end validation (including Soroban resource checks) and introduces new mixed classic+pregen + synthetic Soroban load profiles for exercising overlay throughput without on-ledger contract setup.

Changes:

• Remove the overlay-only checkValid short-circuit and add an overlay-only test-only mechanism to skip seqnum equality checks during validation.
• Add new MIXED_PREGEN_* loadgen modes, including synthetic Soroban transaction generation (SAC payment, OZ token transfer, Soroswap swap) alongside pre-generated classic payments.
• Refactor Soroswap swap tx construction into TxGenerator and improve overlay-only apply logging and tx-set validation behavior in tests.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/transactions/TransactionFrame.cpp	Removes overlay-only checkValid bypass; adds conditional seqnum check skip via ledger-view wrapper flag.
src/ledger/ImmutableLedgerView.h	Adds test-only mSkipSeqNumCheck flag to support overlay-only validation.
src/herder/TransactionQueue.cpp	Sets mSkipSeqNumCheck in overlay-only; adjusts fee-check gating for test builds.
src/herder/TxSetUtils.cpp	Sets mSkipSeqNumCheck for tx-set validation in overlay-only.
src/herder/TxSetFrame.cpp	Disables unique-source enforcement in overlay-only (test-only).
src/herder/HerderImpl.cpp	Disables 1-tx-per-source cross-queue limit in overlay-only (test-only).
src/simulation/LoadGenerator.h / .cpp	Adds MIXED_PREGEN modes, synthetic Soroban tx creation, and per-stream accounting for completion.
src/simulation/TxGenerator.h / .cpp	Adds synthetic contract/state builders and a Soroswap swap tx builder; centralizes key helpers.
src/simulation/ApplyLoad.h / .cpp	Reuses TxGenerator’s Soroswap state/types and swap builder.
src/simulation/test/LoadGeneratorTests.cpp	Updates overlay-only test config limits and adds mixed-mode test coverage.
src/main/CommandHandler.cpp	Adds CLI params for MIXED_PREGEN per-stream TPS and sets combined txRate.
src/ledger/LedgerManagerImpl.cpp	Improves overlay-only “skipping apply” log with classic/soroban breakdown.