[PLAT-756] Add treasury account

[cowboy-bebug]

Description

Changes:

• add a pallet account to hold treasury until claimed by treasurer
• add checks to prevent setting fees too low (lower than ED)
  • this is extremely unlikely but there for safety

Type of changes

• build: Changes that affect the build system or external dependencies (eg, Cargo, Docker)
• ci: Changes to CI configuration
• docs: Changes to documentation only
• feat: Changes to add a new feature
• fix: Changes to fix a bug
• refactor: Changes that do not alter functionality
• style: Changes to format the code
• test: Changes to add missing tests or correct existing tests

Checklist

• Tests for the changes have been added
• Necessary documentation is added (if appropriate)
• Formatted with cargo fmt --all
• Linted with cargo clippy --all-features --all-targets
• Tested with cargo test --workspace --all-features --all-targets

[codecov]

Codecov Report

Patch coverage: 95.00% and project coverage change: +0.15 🎉

Comparison is base (44dbb21) 81.80% compared to head (ab9fc4a) 81.96%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #233      +/-   ##
===========================================
+ Coverage    81.80%   81.96%   +0.15%     
===========================================
  Files           15       15              
  Lines         1072     1087      +15     
===========================================
+ Hits           877      891      +14     
- Misses         195      196       +1     

Impacted Files	Coverage Δ
pallets/ajuna-awesome-avatars/src/lib.rs	88.72% <95.00%> (+0.15%)	⬆️

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