feat: custom chains support

[joepegler]

PR-Codex overview

The focus of this PR is to add support for custom chains in the Biconomy SDK.

Detailed summary

• Added support for custom chains in various modules
• Updated chain configuration options in multiple files
• Implemented custom chain creation utility functions
• Improved file storage handling for sessions
• Enhanced testing with custom chain scenarios

The following files were skipped due to too many changes: src/account/utils/getChain.ts

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[github-actions]

size-limit report 📦

Path	Size
core (esm)	54.37 KB (+0.78% 🔺)
core (cjs)	59.48 KB (+0.64% 🔺)
account (tree-shaking)	52.34 KB (+0.72% 🔺)
bundler (tree-shaking)	2.63 KB (+10.15% 🔺)
paymaster (tree-shaking)	2.33 KB (0%)
modules (tree-shaking)	40.57 KB (-0.07% 🔽)