op-node: add FETCH_WITHDRAWAL_ROOT_FROM_STATE config var

[geoknee]

This was an action item arising from the FMA for the "withdrawals root in block header" feature bundled into Isthmus.

Link: https://github.com/ethereum-optimism/design-docs/blob/1d1ff3a666c1ffba3b8d92e09db08d7efc7234d7/security/fma-withdrawals-root-in-block-header.md?plain=1#L102

• wired up to the L2ClientConfig.
• escape hatch for isthmus behaviour in L2Client.outputV0

Tests

This has been tested locally with kurtosis (set the boolean as an env var, execute cast rpc optimism_outputAtBlock 0x1 --rpc-url http://localhost:53439 | jq .withdrawalStorageRoot and watch the logs for the new log line). I also cross checked an op-node with the flag on with one with the flag off for consistency.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 45.22%. Comparing base (83b1ffc) to head (8049f7f).
Report is 26 commits behind head on develop.

Files with missing lines	Patch %	Lines
op-service/sources/l2_client.go	0.00%	10 Missing ⚠️
op-node/node/node.go	0.00%	2 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (83b1ffc) and HEAD (8049f7f). Click for more details.

HEAD has 8 uploads less than BASE

Flag	BASE (83b1ffc)	HEAD (8049f7f)
cannon-go-tests-32	3	0
cannon-go-tests-64	3	0
	2	1
contracts-bedrock-tests	2	1

Additional details and impacted files

@@             Coverage Diff              @@
##           develop   #15150       +/-   ##
============================================
- Coverage    75.22%   45.22%   -30.01%     
============================================
  Files          184     1149      +965     
  Lines        11481    97248    +85767     
============================================
+ Hits          8637    43980    +35343     
- Misses        2637    50083    +47446     
- Partials       207     3185     +2978     

Flag	Coverage Δ
cannon-go-tests-32	?
cannon-go-tests-64	?
contracts-bedrock-tests	94.35% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
op-node/flags/flags.go	83.33% <ø> (ø)
op-node/node/config.go	0.00% <ø> (ø)
op-node/service.go	0.00% <ø> (ø)
op-node/node/node.go	0.35% <0.00%> (ø)
op-service/sources/l2_client.go	0.00% <0.00%> (ø)

... and 1088 files with indirect coverage changes

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[sebastianst]

thanks, lgtm, just some typo nits