practracker: Accept extra file lines, enforce a smaller function

Accept extra lines in nodelist and routerlist due to extra features, and
due to refactors that simplify some functions.

Most of the refactor eliminated duplicate code in smaller functions, so
there's only one large function that got smaller.

Part of 34200.

scripts/maint/practracker/exceptions.txt

@@ -96,7 +96,7 @@ problem function-size /src/core/or/channeltls.c:channel_tls_process_authenticate
 problem dependency-violation /src/core/or/channeltls.c 11
 problem include-count /src/core/or/circuitbuild.c 53
 problem function-size /src/core/or/circuitbuild.c:get_unique_circ_id_by_chan() 128
-problem function-size /src/core/or/circuitbuild.c:choose_good_exit_server_general() 206
+problem function-size /src/core/or/circuitbuild.c:choose_good_exit_server_general() 196
 problem dependency-violation /src/core/or/circuitbuild.c 25
 problem include-count /src/core/or/circuitlist.c 55
 problem function-size /src/core/or/circuitlist.c:HT_PROTOTYPE() 109
@@ -259,7 +259,7 @@ problem function-size /src/feature/nodelist/node_select.c:router_pick_directory_
 problem function-size /src/feature/nodelist/node_select.c:compute_weighted_bandwidths() 204
 problem function-size /src/feature/nodelist/node_select.c:router_pick_trusteddirserver_impl() 116
 problem function-size /src/feature/nodelist/nodelist.c:compute_frac_paths_available() 190
-problem file-size /src/feature/nodelist/routerlist.c 3300
+problem file-size /src/feature/nodelist/routerlist.c 3350
 problem function-size /src/feature/nodelist/routerlist.c:router_rebuild_store() 148
 problem function-size /src/feature/nodelist/routerlist.c:router_add_to_routerlist() 168
 problem function-size /src/feature/nodelist/routerlist.c:routerlist_remove_old_routers() 121