[release] Add gRPC C++ 1.66 to the interop matrix tests (#37557)

Closes #37557

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/37557 from drfloob:1_66_0-interop_matrix 0807c255e5
PiperOrigin-RevId: 666849683

tools/interop_matrix/client_matrix.py

@@ -135,6 +135,7 @@ LANG_RELEASE_MATRIX = {
             ("v1.63.1", ReleaseInfo()),
             ("v1.64.1", ReleaseInfo()),
             ("v1.65.0", ReleaseInfo()),
+            ("v1.66.0", ReleaseInfo()),
         ]
     ),
     "go": OrderedDict(
@@ -806,6 +807,12 @@ LANG_RELEASE_MATRIX = {
                     runtimes=["python"], testcases_file="python__master"
                 ),
             ),
+            (
+                "v1.66.0",
+                ReleaseInfo(
+                    runtimes=["python"], testcases_file="python__master"
+                ),
+            ),
         ]
     ),
     "node": OrderedDict(
@@ -905,6 +912,7 @@ LANG_RELEASE_MATRIX = {
             ("v1.63.0", ReleaseInfo()),
             ("v1.64.0", ReleaseInfo()),
             ("v1.65.0", ReleaseInfo()),
+            ("v1.66.0", ReleaseInfo()),
         ]
     ),
     "php": OrderedDict(
@@ -968,6 +976,7 @@ LANG_RELEASE_MATRIX = {
             ("v1.63.0", ReleaseInfo()),
             ("v1.64.0", ReleaseInfo()),
             ("v1.65.0", ReleaseInfo()),
+            ("v1.66.0", ReleaseInfo()),
         ]
     ),
     "csharp": OrderedDict(