soroban-rpc: preflight: remove key sizes from read_bytes computation

[2opremio]

Core stopped including including them

Followup from #913 (comment)

[2opremio]

This has unveiled yet another ResourceLimitExceeded error when running the BumpFootprint operation. The test fails at https://github.com/2opremio/soroban-cli/blob/remove-keys-from-fee-estimation/cmd/soroban-rpc/internal/test/simulate_transaction_test.go#L748

envelope: AAAAAgAAAABzdv3ojkzWHMD7KUoXhrPx0GH18vHKV0ZfqpMiEblG1gAAZqAAAAAAAAAABAAAAAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAEAAAAAAAAAGQAAAAAAAAAUAAAAAQAAAAAAAAABAAAABgAAAAFnrAIfzK644FciM7c4L1q7oxCN5UdDC/Y0lL2onFdNaAAAAA8AAAAHQ09VTlRFUgAAAAABAAAAAAAAAAAAAAB0AAAAAAAAAAAAAE5FAAAAARG5RtYAAABAGAKEmnKibE8ikaCWwDf34EbFh3OeWSWc4gnsF0RY8B8+xLuOsB/EgHjf1Ns1/r0WssqDrf3P8zO2H3V9k/8pAA==

The soroban transaction data is the following. My guess is that we are not accounting for the written expiration entries. I will try to fix that.

[2opremio]

Unfortunately, adding the write bytes didn't make the test pass. Here is the new soroban transaction data:

[2opremio]

Now, thinking about it, the write_bytes couldn't be the problem since they were already 0 before this PR. Something else is amiss.

[2opremio]

If you set read_bytes to 128 the test passes but it fails if set to 127 so we are missing 128 - 116 = 12 bytes which I am not sure how to account for.

[2opremio]

The serialized length of an expiration ledger entry is 48, and not 36. This explains the missing 12 bytes :S

I noticed that fees.rs in rs-soroban-env also gets it wrong (@sisuresh I guess you copy-pased it from there) so it should be corrected.

[2opremio]

To be more specific. This prints 48:

	entry2 := xdr.LedgerEntry{
		LastModifiedLedgerSeq: 4,
		Data: xdr.LedgerEntryData{
			Type: xdr.LedgerEntryTypeExpiration,
			Expiration: &xdr.ExpirationEntry{
				KeyHash:             xdr.Hash{},
				ExpirationLedgerSeq: 0,
			},
		},
		Ext: xdr.LedgerEntryExt{},
	}
	bin, err := entry.MarshalBinary()
	assert.NoError(t, err)
	fmt.Println(len(bin))

whereas the Rust code reads

 /// Estimate for any `ExpirationEntry` ledger entry, consisting of a 32-byte
 /// hash of the corresponding entry and 4 bytes for expiration ledger.
const EXPIRATION_ENTRY_SIZE: u32 = 32 + 4;

The calculation above didn't take into account the ledger entry type nor the LastModifiedLedgerSeq field

[2opremio]

This is ready to merge, but let's not do it until @sisuresh / @dmkozh confirm that the EXPIRATION_ENTRY_SIZE fix is correct.

[2opremio]

We still need to update the sdk and soroban-env with the upstream fix once this merges