Declare a smaller gas limit for bounded read-only EVM calls

[turbolent]

Description

Optimize gas usage for read-only calls.

Read-only EVM calls in FlowEVMBridgeUtils all declared FlowEVMBridgeConfig.gasLimit (15,000,000),
including calls whose cost is fixed by the ERC20/ERC721 standards.

The FVM admits an EVM call only if the remaining Cadence computation budget covers the declared
gas limit, not the gas the call consumes. At Mainnet's effort weight for EVM gas, 15,000,000 reserves
~1,603 of the 9,999 units a transaction may spend, so a decimals() read burning ~25k gas can be
refused with ~1,500 units unspent — and the payer cannot buy headroom, since 9,999 is the maximum
limit.

---

For contributor use:

• Targeted PR against main branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the standards mentioned here.
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!