Add the ability to tag circuit instructions

For example, TICK[100ns] instead of TICK or I[DYNAMICDECOUPLE] 2 3 5 instead of I 2 3 5
Stim ignores tags, except for propagating them through circuit transformations
Users can use tags for debugging or to communicate information from tools generating stim circuits to tools consuming them

import stim
circuit = stim.Circuit("""
    R[mlr] 0 1
    TICK[200ns]

    H 0
    TICK[10ns]

    REPEAT[unroll] 3 {
        CZ[adiabatic] 0 1
        TICK[20ns]
    }

    H 0
    TICK[20ns]

    I[DYNAMIC_DECOUPLE_NEW_LATEST_VERSION_5_FINAL_ACTUALLY_FINAL_YXY] 2 3 4 5
    M[include_two_state] 0 1
    DETECTOR[subgraph_2] rec[-1] rec[-2]
""")
assert circuit[0].tag == "mlr"
assert circuit[1].tag == "200ns"
assert circuit[2].tag == ""

Fixes https://github.com/quantumlib/Stim/issues/843

quantumlib / Stim

Add the ability to tag circuit instructions #848