Allow for common consecutive instructions merging in circuit schedule visualization

[RoyElkabetz]

Summary

This PR adds an input flag to the circuit schedule draw_ method which will force instructions merging according the following conditions:

1. instructions must take place on the same channel, same branch and being part of the same instruction group (i.e. measurement, reset, etc')
2. instructions must be temporally continuous

If those two conditions are met, then the instructions will be merged into a single instruction.

This new behavior is set to false by default. For enabling, set merge_common_instructions = True.

Details

Here is a concrete example. Consider the following schedule,

"main,reset_4,Qubit 4,7,64,play\n"
"main,reset_4,Qubit 4,71,108,play\n"
"main,reset_4,AWGR1_0,118,325,capture\n"
"main,reset_4,Qubit 4,179,64,play\n"
"main,reset_4,Qubit 4,243,64,play\n"
"main,reset_4,Qubit 4,577,8,play\n"

in the case where merge_common_instructions = True, the above schedule will become

"main,reset_4,Qubit 4,7,300,play\n"
"main,reset_4,AWGR1_0,118,325,capture\n"
"main,reset_4,Qubit 4,577,8,play\n"

because

"main,reset_4,Qubit 4,7,64,play\n"    ---> t0: 7,   tf = t0 +  64 =  71
"main,reset_4,Qubit 4,71,108,play\n"  ---> t0: 71,  tf = t0 + 108 =  179
"main,reset_4,Qubit 4,179,64,play\n"  ---> t0: 179, tf = t0 +  64 =  243
"main,reset_4,Qubit 4,243,64,play\n"  ---> t0: 243, tf = t0 +  64 =  307

[RoyElkabetz]

With this flag enabled, the following schedule

would become

[ElePT]

Overall, LGTM, I only left a small comment in the reno, and you will need to fix the merge conflict before being able to merge the PR.

[ElePT]

I think that adding the example of how the merge works from the PR description would be really helpful for the release note, this would allow users to reference it in an easier way in the future.

[RoyElkabetz]

Sure, added in c93dc47.