feat(statics): add fiatusd and tfiatusd coins

[emiacc]

Add fiatusd and tfiatusd coins to support fiat backing wallets creation.

STLX-13382

[drew-bitgo]

All of my comments are strictly formatting, no functional changes. Otherwise I Approve. A few questions for the SDK team, as well.

[codecov]

Codecov Report

Merging #2261 (0d68381) into master (6951b40) will increase coverage by 86.13%.
The diff coverage is 100.00%.

❗ Current head 0d68381 differs from pull request most recent head 1750a43. Consider uploading reports for the commit 1750a43 to get more accurate results

@@             Coverage Diff             @@
##           master    #2261       +/-   ##
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+ Coverage        0   86.13%   +86.13%     
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  Files           0      198      +198     
  Lines           0     9686     +9686     
  Branches        0     1436     +1436     
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+ Hits            0     8343     +8343     
- Misses          0      919      +919     
- Partials        0      424      +424     

Flag	Coverage Δ
unit	86.13% <100.00%> (?)

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Impacted Files	Coverage Δ
modules/statics/src/coins.ts	100.00% <ø> (ø)
modules/statics/src/networks.ts	100.00% <ø> (ø)
modules/statics/src/account.ts	79.01% <100.00%> (ø)
...ccount-lib/src/coin/dot/batchTransactionBuilder.ts	71.42% <0.00%> (ø)
modules/account-lib/src/coin/hbar/index.ts	100.00% <0.00%> (ø)
modules/account-lib/src/coin/avaxc/keyPair.ts	100.00% <0.00%> (ø)
modules/account-lib/src/coin/hbar/transaction.ts	92.75% <0.00%> (ø)
modules/account-lib/src/coin/hbar/utils.ts	87.00% <0.00%> (ø)
modules/account-lib/src/coin/sol/transaction.ts	95.10% <0.00%> (ø)
modules/account-lib/src/coin/xrp/keyPair.ts	100.00% <0.00%> (ø)
... and 191 more

[tylerlevine]

seems pretty reasonable. Debatably we should not reuse the account convenience function for creating fiat coin instances and should have a separate one. And maybe even a separate child class from BaseCoin altogether. What do you think?

[tylerlevine]

Careful with the unsafe default here - can this throw MethodNotImplementedError() instead?

[emiacc]

In this case I opt to return the default value since I'm emulating the same behavior as SUSD

[emiacc]

seems pretty reasonable. Debatably we should not reuse the account convenience function for creating fiat coin instances and should have a separate one. And maybe even a separate child class from BaseCoin altogether. What do you think?

Thanks @tylerlevine for your suggestions. I added the new child class and the new factory function to create the Fiat coins.

[tylerlevine]

lgtm