Fix/assign network to dvm address string

[secretnamebasis]

Description

ADDRESS_STRING() in DVM-BASIC calls rpc.NewAddressFromKeys(), which cannot itself determine the current network — rpc can't import globals without a circular dependency — so the resulting address always defaulted to mainnet formatting (dero1...) regardless of whether the node is actually running on testnet or as a simulator. This fix explicitly assigns addr.Mainnet = globals.IsMainnet() after construction, so the address string returned inside a contract matches the network it's actually running on.

Verified independently against a simulator-deployed clone of the live FEED contract (e12689bf2e670ab627c90a24cf6d1a3ad0f6eea80a0cc55c32a0af4bc77ce5d0): a testnet signer's own registration key (STORE(ADDRESS_STRING(SIGNER()), ...)) was stored as dero1... instead of the expected deto1..., while the wallet's own GetAddress() correctly returned deto1... for the same key — confirming the mismatch lives in the DVM builtin, not the wallet.

Same fix as deroproject#192 (same author), carried forward here since that PR is still open/unmerged upstream.

Fixes # (no tracked issue number)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• This will require a HardFork to be enabled

Which part is impacted?

• Wallet
• Daemon
• Miner
• Explorer
• Simulator
• Misc (documentation, comments, text...)

(dvm is shared by both cmd/derod and cmd/simulator, since the simulator embeds the same DVM interpreter.)

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas (single-line, self-explanatory change; no new comments needed)
• My changes generate no new warnings

License

I am contributing & releasing the code under DERO Research License (which can be found here).