Refactor configuration by removing Pangaea network references

[Frozen]

This pull request removes all code, configuration, and references related to the "Pangaea" network from the codebase. This includes eliminating Pangaea from supported network types, bootnode and DNS configuration, sharding schedules, and genesis parameters. The changes help simplify the codebase by removing legacy support for a deprecated network.

The most important changes are:

Removal of Pangaea network support across the codebase:

• Deleted the internal/configs/sharding/pangaea.go file, fully removing the Pangaea sharding schedule implementation.
• Removed the Pangaea network type and all related logic from network type definitions, bootnode/DNS configuration, and chain config selection in files such as internal/configs/node/config.go, internal/configs/node/network.go, internal/configs/bootnode/config.go, and internal/configs/sharding/instance.go. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
• Removed Pangaea from command-line flags, usage messages, and network selection logic in various CLI tools (e.g., cmd/config/flags.go, cmd/bootnode/main.go). [1] [2] [3]
• Eliminated Pangaea-specific handling in chain config and sharding schedule selection logic in core and CLI code (block/factory/factory.go, cmd/config/config.go, cmd/config/dumpdb.go, cmd/harmony/main.go, core/genesis.go). [1] [2] [3] [4] [5]

Cleanup of legacy Pangaea-specific code:

• Removed a one-off Pangaea fix in the block reward accumulator logic in core/blockchain_impl.go.

These changes ensure that the codebase no longer contains any Pangaea-specific logic or configuration, reducing maintenance overhead and potential confusion.

[Frozen]

@copilot remove reference
`? github.com/harmony-one/harmony/block/v3 [no test files]

github.com/harmony-one/harmony/cmd/config [github.com/harmony-one/harmony/cmd/config.test]

cmd/config/flags_test.go:413:58: undefined: nodeconfig.Pangaea`

[Copilot]

@copilot remove reference
`? github.com/harmony-one/harmony/block/v3 [no test files]

github.com/harmony-one/harmony/cmd/config [github.com/harmony-one/harmony/cmd/config.test]

...

Updated in commit f5b5d53: removed the stale nodeconfig.Pangaea reference in cmd/config/flags_test.go and aligned the affected test cases to stressnet/stn.

[Frozen]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved the merge conflicts by merging dev into this branch and fixing the conflict in internal/params/config.go while keeping the Pangaea removal intact. Addressed in commit 208d8230.