Add patched recipe for SOCI: (#4510)

SOCI is the C++ database access library. The SOCI recipe was updated in
Conan Center Index (CCI), and it breaks for our choice of options. This
breakage occurs when you build with a fresh Conan cache (e.g. when you
submit a PR, or delete `~/.conan/data`).

* Add a custom Conan recipe for SOCI v4.0.3
* Update dependency building to handle exporting and installing Snappy
  and SOCI
  * Fix workflows to use custom SOCI recipe
* Update BUILD.md to include instruction for exporting the SOCI Conan
  recipe:
  * `conan export external/soci soci/4.0.3@`

This solution has been verified on Ubuntu 20.04 and macOS.

Context:

* There is a compiler error that the `sqlite3.h` header is not available
  when building soci.
* When package B depends on package A, it finds the pieces it needs by
  importing the Package Configuration File (PCF) that Conan generates
  for package A.
  * Read the CMake written by package B to check that it is importing
    the PCF correctly and linking its exports correctly.
  * Since this can be difficult, it is often more efficient to check
    https://github.com/conan-io/conan-center-index/issues for package B
    to see if anyone else has seen a similar problem.
  * One of the issues points to a problem area in soci's CMake. To
    confirm the diagnosis, review soci's CMake (after any patches are
    applied) in the Conan build directory `build/$buildId/src/`.
  * Review the Conan-generated PCF in
    `build/$buildId/build/$buildType/generators/`.
  * In this case, the problem was likely (re)introduced by
    https://github.com/conan-io/conan-center-index/pull/17026
* If there is a problem in the source or in the Conan recipe, the
  fastest fix is to copy the recipe and either:
  * Add a source patch to fix any problems in the source.
  * Change the recipe to fix any problems in the recipe.
* In this case, this can be done by finding soci's Conan recipe at
  https://github.com/conan-io/conan-center-index/tree/master/recipes/soci
  and then copying the `all` directory as `external/$packageName` in our
  project. Then, make any changes.
  * Test packages can be removed from the recipe folder as they are not
    needed.
  * If adding a patch in the `patches` directory, add a description for
    it to `conandata.yml`.
  * Since `conanfile.py` has no `version` property on the recipe class,
    builders need to pass a version on the command line (like they do
    for our `snappy` recipe).
* Add an example command to `BUILD.md`.

Future work: It may make sense to refer to recipes by revision, by
checking in a lockfile.

.github/workflows/nix.yml

@@ -28,6 +28,8 @@ jobs:
               cxx: /usr/bin/clang++-14
     runs-on: [self-hosted, heavy]
     container: thejohnfreeman/rippled-build-ubuntu:12e19cd9034b
+    env:
+      build_dir: .build
     steps:
       - name: check environment
         run: |
@@ -47,15 +49,10 @@ jobs:
           conan profile update conf.tools.build:compiler_executables='{"c": "${{ matrix.profile.cc }}", "cpp": "${{ matrix.profile.cxx }}"}' default
       - name: checkout
         uses: actions/checkout@v3
-      - name: build dependencies
-        run: |
-          mkdir .build
-          cd .build
-          conan install \
-            --output-folder . \
-            --build missing \
-            --settings build_type=${{ matrix.configuration }} \
-            ..
+      - name: dependencies
+        uses: ./.github/actions/dependencies
+        with:
+          configuration: ${{ matrix.configuration }}
       - name: archive cache
         run: tar -czf conan.tar -C ~/.conan .
       - name: upload cache

.github/workflows/windows.yml

@@ -69,8 +69,10 @@ jobs:
         with:
             path: ${{ steps.conan-cache.outputs.dir }}
             key: ${{ hashFiles('~/.conan/profiles/default', 'conanfile.py', 'external/rocksdb/*', '.github/workflows/windows.yml') }}
-      - name: export Snappy
-        run: conan export external/snappy snappy/1.1.9@
+      - name: export custom recipes
+        run: |
+          conan export external/snappy snappy/1.1.9@
+          conan export external/soci soci/4.0.3@
       - name: install dependencies
         run: |
           mkdir $env:build_dir