[new-hotspot-scheduler] add operator influence and more metrics

[Luffbee]

changes:

• disabled balance hot write by leader.
• add operator influence:
  • pending influence before operator finish
  • zombie influence after operator finish
• more metrics to track hotspot operators

[codecov-io]

Codecov Report

Merging #1713 into new-hotspot-scheduler will decrease coverage by 0.03%.
The diff coverage is 61.26%.

@@                    Coverage Diff                    @@
##           new-hotspot-scheduler    #1713      +/-   ##
=========================================================
- Coverage                  75.71%   75.67%   -0.04%     
=========================================================
  Files                        158      161       +3     
  Lines                      15941    16262     +321     
=========================================================
+ Hits                       12070    12307     +237     
- Misses                      2837     2923      +86     
+ Partials                    1034     1032       -2

Impacted Files	Coverage Δ
server/statistics/region.go	96% <ø> (ø)	⬆️
pkg/cache/cache.go	0% <ø> (ø)	⬆️
server/statistics/hot_cache.go	61.3% <ø> (ø)	⬆️
...ools/pd-simulator/simulator/simutil/case_config.go	0% <0%> (ø)
server/schedulers/metrics.go	100% <100%> (ø)	⬆️
tools/pd-ctl/pdctl/command/config_command.go	73.54% <100%> (+2.24%)	⬆️
server/cluster.go	84.16% <100%> (+1.31%)	⬆️
tools/pd-ctl/pdctl/ctl.go	94.87% <100%> (+10.66%)	⬆️
server/region_syncer/server.go	82.05% <100%> (+0.15%)	⬆️
client/client.go	69.76% <100%> (+3.98%)	⬆️
... and 32 more

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