Check for max allocation

[brianshih1]

Issue: #373

This PR checks to see if the size to allocate the array exceeds the max allocation size. This prevents getting panic: runtime: allocation size out of range when decoding arrays with an invalid size.

This is the code to reproduce the error before the fix:

package main

import "github.com/hamba/avro/v2"

func main() {
	rawSchema := []byte("{\"items\":{\"type\":\"boolean\"},\"type\":\"array\"}")

	schema, _ := avro.ParseBytes(rawSchema)

	data := []byte("\x02\x00\xe9\xe9\xe9\xe9\xe9\xe9\xe9\xe9\x00")
	var container any
	avro.Unmarshal(schema, data, &container)
}

This is the line of code that leads to the error. The size is 29787588086545014 while the maxAlloc size is 281474976710656 (const maxAlloc untyped int = (1 << heapAddrBits) - (1-_64bit)*1)

[nrwiersma]

Thanks for the contribution. Nice catch.