TRST audit fixes for Graph Payments contracts

[tmigone]

This PR addresses the following audit findings:

• TRST-H-1 A payer could bypass the escrow mechanism and avoid payments
• TRST-M-10 A RAV could be collected more than once, leading to double payment
• TRST-CL-1 A payer could bypass the escrow mechanism and avoid payments through the vulnerable collector allowance mapping
• TTRST-L-10 The getBalance() function could revert when balance is lower than tokens thawing
• TRST-M-5 Lack of chunking functionality of new RAVs may cause them to not be processable

[openzeppelin-code]

TRST audit fixes for Graph Payments contracts

Generated at commit: 670fba7cf1538e30a5b38465c51ed30402310e41

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	2 4 0 15 40 61
Dependencies	Critical High Medium Low Note Total	0 0 0 0 0 0

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For more details view the full report in OpenZeppelin Code Inspector