refactor: simplify refresh balance triggers

[kathaypacific]

Description

This PR consolidates the way we are refreshing the token balances. I think we let this evolve organically for some time and it has become buggy and inconsistent.

Currently, before this change:

• we have a bunch of watcher functions that seem overcomplicated (dispatching intermediate actions to trigger other sagas)
• we need to remember to dispatch the fetchTokenBalances action after every flow that initiates a transaction. i think it is probably unavoidable to need to remember to trigger a balance fetch, but currently we dispatch a success action for the flow and a separate action for the balances (the dreaded double dispatch)
• we forget to refresh balances in a bunch of places (e.g. swap flow) which means users can try (and fail) to execute other transactions with outdated balances.

This change:

• remove the fetchTokenBalances action entirely and instead, trigger the balance refresh sagas on specific actions. i've tried to document them all.
• there is a loading state that seems unnecessary in the home reducer, most flows were never allowing this loading state to be set. only the send flow was, i think that's a bug. balance refreshes should be a background task and not affect whether we show or hide the balance....
• define balance refresh as a combination of refreshing token balances, exchange rates (the total balance is wrong if the exchange rate is outdated), positions so trigger all those sagas

Test plan

I should see a network request to refresh token balance, exchange rate, positions, shortcuts when I have:

• completed onboarding
• received a payment (transaction feed updated)
• executed a transaction via any app flow

Related issues

• Related to RET-1241

Backwards compatibility

yes

Network scalability

If a new NetworkId and/or Network are added in the future, the changes in this PR will:

• Continue to work without code changes, OR trigger a compilation error (guaranteeing we find it when a new network is added)

[kathaypacific]

this is the main change

[codecov]

Codecov Report

Attention: Patch coverage is 86.66667% with 4 lines in your changes missing coverage. Please review.

Project coverage is 88.96%. Comparing base (e34ca3b) to head (f9b094b).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fiatExchanges/saga.ts	50.00%	1 Missing ⚠️
src/home/saga.ts	92.30%	1 Missing ⚠️
src/localCurrency/saga.ts	50.00%	1 Missing ⚠️
src/positions/saga.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6232      +/-   ##
==========================================
- Coverage   88.98%   88.96%   -0.02%     
==========================================
  Files         737      737              
  Lines       31449    31423      -26     
  Branches     5828     5521     -307     
==========================================
- Hits        27984    27955      -29     
- Misses       3267     3424     +157     
+ Partials      198       44     -154     

Files with missing lines	Coverage Δ
src/account/saga.ts	75.35% <ø> (-0.35%)	⬇️
src/components/TokenBalance.tsx	97.65% <100.00%> (-0.02%)	⬇️
src/earn/saga.ts	95.65% <ø> (-0.07%)	⬇️
src/import/saga.ts	83.76% <ø> (-0.28%)	⬇️
src/localCurrency/actions.ts	77.77% <ø> (-22.23%)	⬇️
src/localCurrency/reducer.ts	68.42% <ø> (+6.51%)	⬆️
src/redux/migrations.ts	97.08% <100.00%> (+<0.01%)	⬆️
src/redux/store.ts	80.00% <ø> (ø)
src/send/saga.ts	77.01% <ø> (-0.52%)	⬇️
src/tokens/saga.ts	96.82% <100.00%> (+1.44%)	⬆️
... and 8 more

... and 65 files with indirect coverage changes

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