Chore: remove hardcode xcm config

[mclyk]

close #1897

[codecov-commenter]

Codecov Report

Base: 62.12% // Head: 62.05% // Decreases project coverage by -0.07% ⚠️

Coverage data is based on head (c5ab830) compared to base (11e68d6).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1891      +/-   ##
==========================================
- Coverage   62.12%   62.05%   -0.08%     
==========================================
  Files         172      172              
  Lines       18563    18586      +23     
==========================================
  Hits        11533    11533              
- Misses       7030     7053      +23     

Impacted Files	Coverage Δ
pallets/traits/src/xcm.rs	0.00% <0.00%> (ø)
runtime/heiko/src/lib.rs	0.00% <ø> (ø)
runtime/kerria/src/lib.rs	0.00% <ø> (ø)
runtime/parallel/src/lib.rs	0.00% <ø> (ø)
runtime/vanilla/src/lib.rs	0.00% <ø> (ø)

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[GopherJ]

@MrPai it'll be handy to add a command for adding new xcm asset using the four infos (unit per second can be calculated)

Ref: https://github.com/PureStake/xcm-tools

[mclyk]

Sure, will add some off-chain scripts in the next PR to make it more convenient.