Add gas cost for UnpackAny

[chipshort]

breaking for people using a custom Any encoder

Benchmark results:

BenchmarkUnpackAny/garbage_any-8          2235267       521.9 ns/op     136 B/op       4 allocs/op
BenchmarkUnpackAny/single_MsgExec-8       1736608       686.1 ns/op       24 B/op       2 allocs/op
BenchmarkUnpackAny/10000_MsgExec-8        1724133       689.4 ns/op       24 B/op       2 allocs/op
BenchmarkUnpackAny/100000_MsgExec-8       1723904       690.6 ns/op       24 B/op       2 allocs/op

So, it looks like it takes roughly 700ns
Our gas target in CosmWasm uses a target of 1e12 Gas/s = 1e3 Gas/ns. That means:
1e3 Gas/ns * 700ns = 700000 Gas (in CW Gas units)

With the default gas multiplier, it's 5 SDK gas

[pinosu]

Great work! LGTM 👍

[chipshort]

Ok, I added the constant, but also fixed a bug that I forgot to push the fix for: The gas cost (at least according to my benchmark) seems pretty constant and not related to the message size (see numbers above), so it should not be multiplied with the length

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.21%. Comparing base (4c5feae) to head (f85d3f6).
Report is 14 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2115   +/-   ##
=======================================
  Coverage   46.20%   46.21%           
=======================================
  Files          78       78           
  Lines       10810    10811    +1     
=======================================
+ Hits         4995     4996    +1     
  Misses       5368     5368           
  Partials      447      447           

Files with missing lines	Coverage Δ
x/wasm/keeper/handler_plugin_encoders.go	79.47% <100.00%> (+0.06%)	⬆️