eth: Set gas tip to 0 on Arb chains

[yondonfu]

What does this pull request do? Explain your changes. (required)

TODO:

• Consider refactoring to avoid requesting for a chainID every time SuggestGasTipCap is called (i.e. every time a tx is submitted)?

Specific updates (required)

How did you test each of these updates (required)

Does this pull request close any open issues?

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[codecov]

Codecov Report

Merging #2575 (73aaca8) into master (6bf2087) will decrease coverage by 0.04688%.
The diff coverage is 0.00000%.

@@                 Coverage Diff                 @@
##              master       #2575         +/-   ##
===================================================
- Coverage   56.42997%   56.38309%   -0.04688%     
===================================================
  Files             88          88                 
  Lines          18857       18878         +21     
===================================================
+ Hits           10641       10644          +3     
- Misses          7637        7656         +19     
+ Partials         579         578          -1     

Impacted Files	Coverage Δ
eth/backend.go	43.82716% <0.00000%> (-6.52746%)	⬇️
discovery/db_discovery.go	69.67509% <0.00000%> (-1.08304%)	⬇️
server/mediaserver.go	67.28972% <0.00000%> (+0.46729%)	⬆️

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Impacted Files	Coverage Δ
eth/backend.go	43.82716% <0.00000%> (-6.52746%)	⬇️
discovery/db_discovery.go	69.67509% <0.00000%> (-1.08304%)	⬇️
server/mediaserver.go	67.28972% <0.00000%> (+0.46729%)	⬆️

[yondonfu]

SuggestGasTipCap will actually return 0 on Arbitrum so an additional check doesn't seem to be needed.

Also, this PR doesn't actually solve the insufficient funds issue #2574 so closing in favor of #2583