Implement crypto/internal/backend outside of the standard library

[qmuntal]

The crypto backend layer can be moved outside of the standard library. This way the patch files are smaller and changes in the backend will be easier to review. That is, the cryptobackend package is now regular source code.

Note that this PR adds 2500 lines of code, but all of the additions are in patches/0001-Vendor-external-dependencies.patch, which is automatically generated by copying the external dependencies, like now the cryptobackend package. On the other hand, patches/0002-Add-crypto-backends.patch loses 2500 lines of code, and that's the real win, given that all these lines were real code.

[Copilot]

Pull request overview

Moves the system crypto backend implementation out of crypto/internal/* and into a standalone module (github.com/microsoft/go/cryptobackend) that is vendored into GOROOT/src/vendor, reducing patch churn and making backend changes easier to review.

Changes:

• Introduces the new cryptobackend/ module (backend shims, FIPS state detection, OpenSSL init helper, tests) and wires it into the build via vendoring.
• Updates the vendor patch to include the vendored github.com/microsoft/go/cryptobackend tree and adjusts dependency tracking (src/crypto/deps_ignore.go, src/go.mod, modules.txt, etc.).
• Updates TLS-related patching and repository guidance/docs to use the new backend import path.

Patches are happy!

Show a summary per file

File	Description
patches/0010-Align-TLS-settings-with-Microsoft-policies.patch	Updates TLS policy patch to use the externalized backend and related toggles.
patches/0001-Vendor-external-dependencies.patch	Vendors the new github.com/microsoft/go/cryptobackend package and updates std module deps accordingly.
eng/_util/internal/patchcheck/vendoronly.go	Adjusts vendor-only path allowlist for moved deps ignore file.
cryptobackend/stub.s	Stub assembly file to satisfy tooling/link expectations for runtime_arg0.
cryptobackend/README.md	Documents how/why cryptobackend is vendored and the stdlib-only import exceptions.
cryptobackend/nobackend.go	Non-systemcrypto stubs for the backend package.
cryptobackend/internal/opensslsetup/stub.go	Placeholder package file for OpenSSL setup support.
cryptobackend/internal/opensslsetup/opensslsetup_linux.go	Linux OpenSSL library discovery/initialization helper.
cryptobackend/internal/opensslsetup/opensslsetup_linux_test.go	Unit tests for OpenSSL library selection logic.
cryptobackend/internal/fips140state/systemfips_windows.go	Windows system FIPS detection.
cryptobackend/internal/fips140state/systemfips_linux.go	Linux system/kernel/OpenSSL FIPS detection.
cryptobackend/internal/fips140state/systemfips_darwin.go	Darwin system FIPS detection stub.
cryptobackend/internal/fips140state/state.go	Core FIPS enablement detection and backend checks.
cryptobackend/internal/fips140state/state_test.go	Tests for FIPS detection logic.
cryptobackend/internal/fips140state/state_nomsgostd.go	Non-stdlib build behavior for reading GODEBUG setting.
cryptobackend/internal/fips140state/state_msgostd.go	Stdlib-only behavior for reading GODEBUG setting.
cryptobackend/internal/fips140state/skipfipscheck_on.go	Build-tag hook to skip FIPS checks.
cryptobackend/internal/fips140state/skipfipscheck_off.go	Default behavior when skip tag is not set.
cryptobackend/internal/fips140state/requirefips_nosystemcrypto.go	requirefips handling when systemcrypto isn’t enabled.
cryptobackend/internal/fips140state/nosystemcrypto.go	System FIPS detection stub when systemcrypto is off.
cryptobackend/internal/fips140state/norequirefips.go	Default requirefips flag state.
cryptobackend/internal/fips140state/isrequirefips.go	requirefips flag state under build tag.
cryptobackend/go.sum	Module sums for backend dependencies.
cryptobackend/go.mod	Declares the standalone github.com/microsoft/go/cryptobackend module.
cryptobackend/fips140/fips140.go	Public shim API for querying FIPS enablement.
cryptobackend/common.go	Shared helpers (FIPS check plumbing, unreachable guards).
cryptobackend/bbig/big.go	Non-systemcrypto stub bbig API.
cryptobackend/bbig/big_windows.go	Windows bbig wiring for systemcrypto builds.
cryptobackend/bbig/big_linux.go	Linux bbig wiring for systemcrypto builds.
cryptobackend/bbig/big_darwin.go	Darwin bbig wiring for systemcrypto builds.
cryptobackend/backend_windows.go	Windows backend implementation wiring (CNG).
cryptobackend/backend_windows_msgostd.go	Stdlib-only Windows glue (msgostd) for backend integration.
cryptobackend/backend_test.go	Tests for backend helper behavior.
cryptobackend/backend_linux.go	Linux backend implementation wiring (OpenSSL).
cryptobackend/backend_darwin.go	Darwin backend implementation wiring (CryptoKit/CommonCrypto).
.vscode/settings.json	Adds VS Code Go environment/debug defaults for this repo.
.github/instructions/patch-consistency.instructions.md	Updates patch consistency guidance for moved deps ignore path.
.github/copilot-instructions.md	Updates repository Copilot guidance to use the new backend import path.

Copilot's findings

• Files reviewed: 37/40 changed files
• Comments generated: 5

[gdams]

Love this!