Build wasmtime with wasmtime-c-api-impl crate (#501)

Always uses prefixed wasmtime-c-api-impl, otherwise the prefixed
implementation bitrots. Prefixes the headers in the repo rule to allow
for globbing, which is not possible in a genrule.

The crates_vendor-provided wasmtime-c-api-impl provided build allows us
to upgrade wasmtime solely by changing the version number in the
repositories.bzl and Cargo.toml files.

Build off of #496

---------

Signed-off-by: Matt Leon <mattleon@google.com>

Author: leonm1

BUILD

@@ -187,45 +187,6 @@ cc_library(
     ],
 )
 
-cc_library(
-    name = "wasmtime_lib",
-    srcs = [
-        "src/common/types.h",
-        "src/wasmtime/types.h",
-        "src/wasmtime/wasmtime.cc",
-    ],
-    hdrs = ["include/proxy-wasm/wasmtime.h"],
-    copts = [
-        "-DWASM_API_EXTERN=",
-    ],
-    defines = [
-        "PROXY_WASM_HAS_RUNTIME_WASMTIME",
-        "PROXY_WASM_HOST_ENGINE_WASMTIME",
-    ],
-    # See: https://bytecodealliance.github.io/wasmtime/c-api/
-    linkopts = select({
-        "@platforms//os:macos": [],
-        "@platforms//os:windows": [
-            "ws2_32.lib",
-            "advapi32.lib",
-            "userenv.lib",
-            "ntdll.lib",
-            "shell32.lib",
-            "ole32.lib",
-            "bcrypt.lib",
-        ],
-        "//conditions:default": [
-            "-ldl",
-            "-lm",
-            "-lpthread",
-        ],
-    }),
-    deps = [
-        ":wasm_vm_headers",
-        "@com_github_bytecodealliance_wasmtime//:wasmtime_lib",
-    ],
-)
-
 genrule(
     name = "prefixed_wasmtime_sources",
     srcs = [
@@ -239,15 +200,14 @@ genrule(
     cmd = """
         for file in $(SRCS); do
            sed -e 's/wasm_/wasmtime_wasm_/g' \
-               -e 's/include\\/wasm.h/include\\/prefixed_wasm.h/g' \
                -e 's/wasmtime\\/types.h/wasmtime\\/prefixed_types.h/g' \
-           $$file >$(@D)/$$(dirname $$file)/prefixed_$$(basename $$file)
+           $$file >$(@D)/src/wasmtime/prefixed_$$(basename $$file)
         done
         """,
 )
 
 cc_library(
-    name = "prefixed_wasmtime_lib",
+    name = "wasmtime_lib",
     srcs = [
         "src/common/types.h",
         "src/wasmtime/prefixed_types.h",
@@ -281,7 +241,7 @@ cc_library(
     }),
     deps = [
         ":wasm_vm_headers",
-        "@com_github_bytecodealliance_wasmtime//:prefixed_wasmtime_lib",
+        "@com_github_bytecodealliance_wasmtime//:wasmtime_lib",
     ],
 )
 
@@ -299,6 +259,5 @@ cc_library(
         [":wasmedge_lib"],
     ) + proxy_wasm_select_engine_wasmtime(
         [":wasmtime_lib"],
-        [":prefixed_wasmtime_lib"],
     ),
 )