Expand test suite to cover different combinations of `#SECTION` and `#BRANCHSTART`

[vivaria]

Songs with basic usage (#SECTION before #BRANCHSTART) convert OK!

However, I have a feeling I don't cover every case... for example, take the ESE chart for Taiko Time:

#BRANCHSTART p,80,98.5
#N
#SECTION
#GOGOSTART
#BPMCHANGE 170
[...]
#E
#SECTION
#GOGOSTART
#BPMCHANGE 170
[...]
#M
#GOGOSTART
#SECTION
#BPMCHANGE 170
[...]
#BRANCHSTART p,80,90

Here, #SECTION comes after the #N/#E/#M commands, and there are two different #BRANCHSTART p commands. So, I'm very curious what the branch_info bytes will be in an official fumen, and whether my converter produces the correct bytes.

Other songs to test:

• [ ] Taiko Time
• [ ] Dragon Night (has #BRANCHSTART but no #SECTION... though, song has percentage conditions, so I guess #SECTION doesn't matter?)
• [ ] Soroban 2000 (has #BRANCHSTART p,-1,0.0001)

My question is: Do any custom charters do weird things with #SECTION/#BRANCHSTART? Like, for example:

• Have #BRANCHSTART r with no #SECTION so that there is a cumulative drumroll count
• Have #BRANCHSTART p with no #SECTION so that the percentage is an average of all #BRANCHSTART commands

Or, is this behavior so niche that no one ever bothers?

[vivaria]

DDDDDD has reported two new songs that fail due to #SECTION/#BRANCHSTART. I will need to figure out why:

• clsn.zip
• tktime.zip

[vivaria]

I've made some changes in tja2fumen 0.7.1 that will hopefully address some additional crashes due to #SECTION commands.

I'm not confident enough to mark this as fixed, but I do think things have improved. :)