[mbrandenburger]

What this PR does / why we need it:
Since #1048 the C/C++ side is opt-in (FPC_CGO=1), but its code was spread across the tree: common/, ecc_enclave/, cmake/, the cgo files in ecc/ and internal/, the C++ samples, irb's chaincode and the shell integration suites. This PR moves all of it under one directory, sgx/, so the code that needs the SGX toolchain is in one place. No behavior changes.

From	To
common/ (incl. the common/crypto/pdo submodule)	sgx/common/
ecc_enclave/	sgx/ecc_enclave/
cmake/	sgx/cmake/
samples/chaincode/{auction,echo,kv-test}/	sgx/samples/chaincode/…
samples/demos/irb/chaincode/	sgx/samples/demos/irb/chaincode/ (irb's Go app and protos stay)
integration/*_test.sh, integration/{config,crashtest,client_sdk}/	sgx/integration/… (integration/go_chaincode/ stays)
internal/attestation/epid/pdo/	sgx/attestation/epid/pdo/
the real enclave (ecc/chaincode/enclave/{enclave,shim,logging_cgo,logging_go}.go)	sgx/ecc/enclave/ (the mock stays)

What stays: ecc/, fabric/, protos/, irb's Go app, integration/go_chaincode/, and the PDO crypto in internal/crypto/ (its test is coupled to the shared crypto test table; only its #cgo paths change).

Which issue(s) this PR fixes:
Fixes #1041. Part of #1044.

Special notes for your reviewer:
Three commits, best reviewed one by one (please rebase-merge, so git log --follow works):

1. Moves only. git mv, 167 files renamed with identical content, and the .gitmodules path that git updates. The tree does not build at this commit.
2. The enclave split, the only code change. ecc/main.go picks the enclave through newEnclave() in two tagged files, ecc/enclave_cgo.go (fpc_cgo, the real one from sgx/ecc/enclave) and ecc/enclave_mock.go (!fpc_cgo, the mock). scripts/check-ecc-enclave.sh checks which one ecc uses with and without the tag.
3. Path fixes. Makefiles (the top level keeps the old build order, with sgx/... in place of each moved part), CMake and script $ENV{FPC_PATH} paths, #cgo paths, the moved shell suites (one level deeper), Go filepath.Join paths and the moved utils import, the committed symlinks, Dockerfiles, irb, and docs.

How I checked the move is complete:

• A scratch script greps every old path (anchored, so samples/chaincode/echo doesn't match echo-go), the Go filepath.Join segment form, Go imports of moved packages, and dangling symlinks. The remaining hits are not paths: the ecc_enclave component and logger name, make target names, and the linter and license excludes, which match as substrings and still work.
• A fresh git clone --recursive populates sgx/common/crypto/pdo and builds.
• Natively (Mac): go build/vet/test ./..., make build test checks, and the check-* scripts pass.

Left as they were, because changing them would change behavior: ecc/Makefile's clean removes enclave/ecc-enclave-{lib,include}, a path that never existed (the links are committed, so actually removing them would leave the tree dirty); sgx/ecc_enclave/CMakeLists.txt sets an unused DEPLOY_DIR.

Does this PR introduce a user-facing changes and/or breaks backward compatability?:
Yes, paths change. For out-of-tree C++ chaincode and scripts:

Old	New
$FPC_PATH/cmake/	$FPC_PATH/sgx/cmake/
$FPC_PATH/ecc_enclave/ (e.g. enclave/CMakeLists-common-app-enclave.txt)	$FPC_PATH/sgx/ecc_enclave/
$FPC_PATH/common/	$FPC_PATH/sgx/common/
$FPC_PATH/integration/config/	$FPC_PATH/sgx/integration/config/
$FPC_PATH/samples/chaincode/{auction,echo,kv-test}/	$FPC_PATH/sgx/samples/chaincode/…

Go: internal/attestation/epid/pdo (internal, so only used in this repo) is now sgx/attestation/epid/pdo, and the real enclave package ecc/chaincode/enclave is now sgx/ecc/enclave (ecc/chaincode/enclave keeps the mock). Existing build directories (_build) under the old paths have to be rebuilt.