deployment: extract base-layer start-block numbers into shared constants

[nimrod-starkware]

Extract the six per-env base-layer L1 start-block numbers (bpo1, bpo2,
fusaka_no_bpo) into configs/base_layer_constants.libsonnet, shared across
the sepolia envs (SEPOLIA_* used by sepolia-alpha and sepolia-integration)
and mainnet (MAINNET_*), imported by each env's chain_params.jsonnet.

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

[reviewable-StarkWare]

This change is 

[nimrod-starkware]

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• deployment: move all jsonnet files together #14806
• deployment,scripts: remove dead configList config key #14804
• apollo_reverts: make RevertConfig a newtype wrapping Option<BlockNumber> #14701
• apollo_deployments: delete Rust component-config topology mirror #14688
• apollo_deployments,apollo_integration_tests: source harness component configs from jsonnet #14687
• deployment: drop redundant YAML sequencerConfig; source port-uniqueness from jsonnet #14659
• apollo_config,workspace: remove SerializeConfig trait and preset-dump machinery #14654
• apollo_config,apollo_node_config,apollo_config_manager: rework get_config_presentation off dump() #14653
• apollo_node_config,apollo_node: delete CONFIG_POINTERS data and pointer-remap from secrets bin #14652
• apollo_node_config,apollo_config_manager,apollo_integration_tests: retire preset config-generation path #14651
• apollo_node_config: promote normalize_pointer_groups to shared config_utils test helper #14731
• apollo_node_config,apollo_deployments: assert cross-component equality for formerly-pointer-resolved fields #14650
• apollo_deployments: delete base app_configs and the preset-parity test machinery #14649
• apollo_node_config,apollo_node,deployment: source private_parameters from secrets schema, drop value config schema #14648
• apollo_deployments: retire dead preset/replacer generation machinery #14647
• deployment,apollo_deployments: drop config_format plumbing and retire preset config path #14646
• deployment: add native config layers for the testing overlays #14645
• deployment: add dummy_for_testing native config override layer #14632
• apollo_config: make native the sole config-load path #14631
• apollo_integration_tests,apollo_node_config: load integration-test node config via native format #14629
• apollo_config,apollo_node_config: make config fields with custom deserializers serialize symmetrically #14630
• apollo_deployments: expose jsonnet build() evaluator behind a testing feature #14686
• deployment: extract base-layer start-block numbers into shared constants #14685 👈 (View in Graphite)
• deployment: add mainnet native config override layer #14628
• deployment: add sepolia-alpha native config override layer #14627
• deployment: add sepolia-integration native config override (chain_params + replacers) #14674 : 1 other dependent PR (#14626 )
• deployment: add native node-config builder and wire it into the ConfigMap #14609 : 1 other dependent PR (#14655 )
• deployment: thread config_format from CLI to node container arg #14608
• apollo_deployments,deployment: set storage-reader-server ports as constants #14607
• apollo_node: add new CLI arg to parse config #14606
• apollo_deployments: check applicative config matches deployed app_configs #14489 : 2 other dependent PRs (#14480 , #14505 )
• apollo_deployments: assemble and deserialize node config from jsonnet #14487
• apollo_deployments: assemble full node config via build.libsonnet #14486
• apollo_deployments: distributed layout jsonnet test #14485
• apollo_deployments: consolidated layout jsonnet test #14484
• apollo_deployments: test hybrid layout for infra config #14483
• apollo_deployments: introduce hybrid layout for infra config #14482
• apollo_deployments: introduce jsonnet building blocks for infra config #14481
• apollo_deployments: jsonnet applicative config #14479
• main

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[nimrod-starkware]

@nimrod-starkware reviewed 4 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on dan-starkware and matanl-starkware).