types: use (*math/big.Int).BitLen() == 0 to check if value is 0

[odeke-em]

Instead of using len((*math/big.Int).Bytes()) == 0, which expensively
creates a byte slice and marshals a value, on the majority hot path,
instead use the cheaper method .BitLen() to check if 0.

Benchmarking results, just from types:

name                                           old time/op    new time/op    delta
CoinsAdditionIntersect/sizes:_A_1,_B_1-8          132ns ± 2%     126ns ±13%   -4.55%  (p=0.050 n=10+10)
CoinsAdditionIntersect/sizes:_A_5,_B_5-8         1.41µs ± 3%    1.41µs ± 2%     ~     (p=1.000 n=10+10)
CoinsAdditionIntersect/sizes:_A_5,_B_20-8        2.30µs ± 1%    2.27µs ± 3%     ~     (p=0.066 n=10+10)
CoinsAdditionIntersect/sizes:_A_1,_B_1000-8      30.9µs ± 3%    30.7µs ± 1%     ~     (p=0.218 n=10+10)
CoinsAdditionIntersect/sizes:_A_2,_B_1000-8      31.4µs ± 3%    30.8µs ± 2%   -1.94%  (p=0.015 n=10+10)
CoinsAdditionNoIntersect/sizes:_A_1,_B_1-8        116ns ± 1%     114ns ± 4%     ~     (p=0.142 n=10+10)
CoinsAdditionNoIntersect/sizes:_A_5,_B_5-8       1.11µs ± 1%    1.08µs ± 3%   -2.36%  (p=0.003 n=8+10)
CoinsAdditionNoIntersect/sizes:_A_5,_B_20-8      1.85µs ± 2%    1.82µs ± 1%   -1.38%  (p=0.001 n=10+9)
CoinsAdditionNoIntersect/sizes:_A_1,_B_1000-8    30.7µs ± 1%    30.6µs ± 3%     ~     (p=0.393 n=10+10)
CoinsAdditionNoIntersect/sizes:_A_2,_B_1000-8    31.1µs ± 1%    30.7µs ± 2%   -1.32%  (p=0.015 n=10+10)
CoinsAdditionNoIntersect/sizes:_A_1000,_B_2-8    31.0µs ± 2%    30.7µs ± 2%     ~     (p=0.190 n=10+10)
Bech32ifyPubKey-8                                28.8µs ± 5%    28.8µs ± 3%     ~     (p=0.965 n=10+8)
GetPubKeyFromBech32-8                            38.8µs ± 3%    39.4µs ± 2%   +1.70%  (p=0.013 n=9+10)
ParseCoin-8                                      16.7µs ± 6%    15.8µs ± 4%   -5.21%  (p=0.001 n=10+10)
MarshalTo-8                                       521ns ± 5%     508ns ± 3%   -2.56%  (p=0.029 n=10+10)
UintMarshal-8                                    3.10µs ±17%    2.56µs ± 3%  -17.45%  (p=0.000 n=10+9)
IntMarshal-8                                     2.52µs ±10%    1.94µs ± 2%  -23.10%  (p=0.000 n=10+10)

name                                           old alloc/op   new alloc/op   delta
Bech32ifyPubKey-8                                4.02kB ± 0%    4.02kB ± 0%     ~     (all equal)
GetPubKeyFromBech32-8                            2.48kB ± 0%    2.48kB ± 0%     ~     (all equal)
ParseCoin-8                                      2.21kB ± 0%    2.21kB ± 0%     ~     (all equal)
MarshalTo-8                                       80.0B ± 0%     80.0B ± 0%     ~     (all equal)
UintMarshal-8                                      440B ± 0%      392B ± 0%  -10.91%  (p=0.000 n=10+10)
IntMarshal-8                                       216B ± 0%      168B ± 0%  -22.22%  (p=0.000 n=10+10)

name                                           old allocs/op  new allocs/op  delta
Bech32ifyPubKey-8                                  25.0 ± 0%      25.0 ± 0%     ~     (all equal)
GetPubKeyFromBech32-8                              85.0 ± 0%      85.0 ± 0%     ~     (all equal)
ParseCoin-8                                        71.0 ± 0%      71.0 ± 0%     ~     (all equal)
MarshalTo-8                                        2.00 ± 0%      2.00 ± 0%     ~     (all equal)
UintMarshal-8                                      31.0 ± 0%      25.0 ± 0%  -19.35%  (p=0.000 n=10+10)
IntMarshal-8                                       24.0 ± 0%      18.0 ± 0%  -25.00%  (p=0.000 n=10+10)

name                                           old speed      new speed      delta
UintMarshal-8                                  2.27MB/s ±15%  2.75MB/s ± 2%  +20.87%  (p=0.000 n=10+8)
IntMarshal-8                                   2.78MB/s ± 9%  3.60MB/s ± 2%  +29.69%  (p=0.000 n=10+10)

Fixes #8575

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #8580 (41b9fe2) into master (e306e5b) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #8580      +/-   ##
==========================================
+ Coverage   61.43%   61.46%   +0.02%     
==========================================
  Files         656      656              
  Lines       37533    37526       -7     
==========================================
+ Hits        23059    23064       +5     
+ Misses      12065    12053      -12     
  Partials     2409     2409              

Impacted Files	Coverage Δ
types/int.go	72.53% <100.00%> (+2.11%)	⬆️
types/uint.go	81.73% <100.00%> (+5.76%)	⬆️
client/grpc_query.go	28.26% <0.00%> (-0.91%)	⬇️
baseapp/grpcserver.go	2.56% <0.00%> (-0.14%)	⬇️
server/grpc/server.go	62.50% <0.00%> (ø)
baseapp/grpcrouter.go	86.04% <0.00%> (+6.04%)	⬆️

[alessio]

I've requested just the addition of a test case; looks good otherwise (and please feel free to dismiss my review once the test case is added)

[odeke-em]

I've requested just the addition of a test case; looks good otherwise (and please feel free to dismiss my review once the test case is added)

Thank you for the review @alessio! I've added the tests, please take a look.

Addressed comments in review.

[tac0turtle]

LGTM, thank you for the PR