issue-metadata: collapse -tracker and -needs resolution

[samuelweiler]

collapsing the five pairs of horizontal labels will help make this doc more usable.

for -tracker:

"Applied by WGs to bring an issue to the attention of a horizontal group. May also be applied by a horizontal group to indicate that they are interested in a discussion. Does not need to be resolved before transition."

for -needs-resolution:

"The horizontal group expects this issue to be resolved to their satisfaction before a transition. (Typically) only applied by horizontal groups, and only removed by them."

[samuelweiler]

@plehegar

[samuelweiler]

Also need to explain that tooling will adjust these.

"-needs-resolution implies -tracking. When -needs-resolution is set, automatic tooling will remove -tracking. That update could take N hours. [how often does the tool run?]"

[samuelweiler]

clarify: if a horizontal group closes a tracking issue and you think they should still pay attention - maybe they missed something then do [something]