remove dependency on golang.org/exp

[ucwong]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.24%. Comparing base (0e6e4cb) to head (408efeb).
Report is 33 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1952      +/-   ##
==========================================
- Coverage   47.26%   47.24%   -0.03%     
==========================================
  Files         568      568              
  Lines       68849    68849              
==========================================
- Hits        32541    32527      -14     
- Misses      33778    33786       +8     
- Partials     2530     2536       +6     

Files	Coverage Δ
accounts/keystore/account_cache.go	87.11% <ø> (-1.85%)	⬇️
cmd/devp2p/dns_route53.go	47.69% <ø> (ø)
cmd/devp2p/nodeset.go	0.00% <ø> (ø)
common/prque/lazyqueue.go	92.59% <100.00%> (ø)
common/prque/prque.go	65.00% <100.00%> (ø)
common/prque/sstack.go	100.00% <100.00%> (ø)
consensus/clique/snapshot.go	79.22% <ø> (ø)
core/blockchain.go	22.86% <ø> (ø)
core/forkid/forkid.go	61.81% <ø> (ø)
core/rawdb/accessors_chain.go	44.24% <ø> (ø)
... and 11 more

... and 9 files with indirect coverage changes