[braket] Add support for observe API (#2539)

Signed-off-by: Pradnya Khalate <pkhalate@nvidia.com>

python/tests/backends/test_braket.py

@@ -101,7 +101,7 @@ def single_qubit_gates():
         s(q)
         t(q)
         mx(q)
-        my(q)
+        ## my(q) # not supported since the default rewriter uses `sdg`
         mz(q)
 
     # Test here is that this runs
@@ -245,17 +245,13 @@ def ansatz(theta: float):
         x(qreg[0])
         ry(theta, qreg[1])
         x.ctrl(qreg[1], qreg[0])
-        ## NOTE: Measure required since 'Device requires all qubits in the program to be measured.'
-        mz(qreg)
 
     # Define its spin Hamiltonian.
     hamiltonian = 5.907 - 2.1433 * spin.x(0) * spin.x(1) - 2.1433 * spin.y(
         0) * spin.y(1) + .21829 * spin.z(0) - 6.125 * spin.z(1)
 
-    with pytest.raises(RuntimeError) as e:
-        cudaq.observe(ansatz, hamiltonian, .59, shots_count=100)
-    assert "observe specification violated for 'ansatz': kernels passed to observe cannot have measurements specified." in repr(
-        e)
+    res = cudaq.observe(ansatz, hamiltonian, .59, shots_count=1)
+    print(res.expectation())
 
 
 def test_custom_operations():

runtime/common/BaseRemoteRESTQPU.h

@@ -547,6 +547,8 @@ class BaseRemoteRESTQPU : public cudaq::QPU {
         for (auto &pass : csvSplit)
           if (pass.ends_with("-gate-set-mapping"))
             runPassPipeline(pass, tmpModuleOp);
+        if (!emulate && combineMeasurements)
+          runPassPipeline("func.func(combine-measurements)", tmpModuleOp);
         modules.emplace_back(term.to_string(false), tmpModuleOp);
       }
     } else