Allow overriding sandbox execution timeout value for an individual guest function call

[danbugs]

When creating an UninitializedSandbox, you can specify a maximum execution time for guest functions:

hyperlight/src/hyperlight_host/src/sandbox/config.rs

Lines 60 to 68 in b9c67fb

	/// The max_execution_time of a guest execution in milliseconds. If set to 0, the max_execution_time
	/// will be set to the default value of 1000ms if the guest execution does not complete within the time specified
	/// then the execution will be cancelled, the minimum value is 1ms
	///
	/// Note: this is a C-compatible struct, so even though this optional
	/// field should be represented as an `Option`, that type is not
	/// FFI-safe, so it cannot be.
	///
	max_execution_time: u16,

This applies to all guest functions and there is currently no way of changing it after initialization. This issue proposes that we should allow users to override the sandbox default for individual guest function calls.

[syntactically]

Closing in favour of #243, which will hopefully remove this timeout API entirely.