Fix: ArrayPool buffer leak in PatriciaTree Get methods

[gitToki]

Changes

• Fixed ArrayPool buffer leak in Get() method - Moved ArrayPool<byte>.Shared.Return(array) from try block to finally block to ensure cleanup even when TrieException is thrown
• Fixed ArrayPool buffer leak in GetNodeByKey() method - Moved ArrayPool<byte>.Shared.Return(array) from try block to finally block to ensure cleanup even when TrieException is thrown

To give a little bit more detail about the why, the Get() and GetNodeByKey() methods in PatriciaTree rent buffers from ArrayPool but only returned them in the success path.

When GetNew() throws a TrieException, the rented buffers weren't returned to the pool, it could've cause gradual memory pressure under sustained load (even if the array get GC'ed at some point).

This was only affecting RPC endpoints when handling requests with keys larger than the 64byte stack allocation min.
For the p2p path, the peer would be banned before causing any significant harm.

[emlautarom1]

The code does not compile as it is:

  Nethermind.Trie failed with 2 error(s) (0.2s)
    /home/emlautarom1/Development/Nethermind/nethermind/src/Nethermind/Nethermind.Trie/PatriciaTree.cs(362,21): error CS0103: The name 'array' does not exist in the current context
    /home/emlautarom1/Development/Nethermind/nethermind/src/Nethermind/Nethermind.Trie/PatriciaTree.cs(362,70): error CS0103: The name 'array' does not exist in the current context

[emlautarom1]

There is a similar case:

nethermind/src/Nethermind/Nethermind.Trie/PatriciaTree.cs

Line 487 in ae427a1

: array = ArrayPool<byte>.Shared.Rent(nibblesCount))

nethermind/src/Nethermind/Nethermind.Trie/PatriciaTree.cs

Line 498 in ae427a1

if (array is not null) ArrayPool<byte>.Shared.Return(array);

If you fix it then we can proceed.

[gitToki]

Thanks for the review