Correct the data type of certain fields to store the expected design values.

[overcat]

Closes #494, Closes #499

#487 depends on this PR.

xdrgen-related PR is in stellar/xdrgen#163

This PR includes breaking changes.

The types of the following fields have changed.

field	before	after
LedgerBounds.minLedger	int	long
LedgerBounds.maxLedger	int	long
MemoId.id	long	BigInteger
TimeBounds.minTime	long	BigInteger
TimeBounds.maxTime	long	BigInteger
TransactionBuilder.baseFee	int	long
TransactionPreconditions.TIMEOUT_INFINITE	long	BigInteger
TransactionPreconditions.minSeqAge	Long	BigInteger
TransactionPreconditions.minSeqLedgerGap	int	long

[overcat]

I have added some TODO items and I am considering whether to complete them in this PR, but it would bring breaking changes.

[sreuland]

@overcat , I'm starting review, I've looked at stellar/xdrgen#163, and it seems ok but I asked for other reviewers on that one as I don't have much experience there.

[sreuland]

one small suggestion, could you update the docs for xdr generation in readme.md to reflect the latest command needed to run, I'm not sure it's current for the new soroban .x files ?

[overcat]

one small suggestion, could you update the docs for xdr generation in readme.md to reflect the latest command needed to run, I'm not sure it's current for the new soroban .x files ?

This command is already up to date, but if you want to generate the xdr classes in this PR, you need to merge the following four PRs.

[sreuland]

the updates look fine, before merging can you respond to the comment about BigInteger conversions to longs here:

https://github.com/stellar/java-stellar-sdk/pull/498/files#r1285301854

thanks!

[sreuland]

the changes look good, one remaining discussion of overflow on datetime's from the xdr HyperIntegers - #498 (comment)

once that is resolved, we can merge?