fix: prevent spamming blockchain.info with requests

[dpc]

In some circumstances, possibly triggered by a bug or unrelated failure it seems possible
for us to keep calling blockstream.info (or other electrs/esplora backend) from the autocommit loop.

I identified two orthogonal improvements:

• watch needs to be called only once, so calling it again on retries is a waste of time
• watch & get are two separate operations so should be treated as such

Each of them separately is effectively fixing the problem we witnessed, but both make sense, so I guess makes sense to land both.

[codecov]

Codecov Report

Attention: 20 lines in your changes are missing coverage. Please review.

Comparison is base (78db6f6) 57.02% compared to head (6044193) 57.01%.

Files	Patch %	Lines
fedimint-bitcoind/src/lib.rs	0.00%	5 Missing ⚠️
fedimint-bitcoind/src/bitcoincore.rs	0.00%	4 Missing ⚠️
fedimint-bitcoind/src/electrum.rs	0.00%	4 Missing ⚠️
fedimint-bitcoind/src/esplora.rs	0.00%	4 Missing ⚠️
modules/fedimint-wallet-client/src/deposit.rs	72.72%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3969      +/-   ##
==========================================
- Coverage   57.02%   57.01%   -0.01%     
==========================================
  Files         193      193              
  Lines       43143    43166      +23     
==========================================
+ Hits        24603    24612       +9     
- Misses      18540    18554      +14     

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[elsirion]

The second commit is an improvement, the first idk, a bit of complexity for not a whole lot of gain imo.

[dpc]

I think what we've observed was actually caused be accumulating multiple deposit addresses. Created a separate issue in: #3970

[elsirion]

Will be hit after about 100k years, sgtm.