make leveldb configurable

[gzliudan]

Proposed changes

make leveldb can be configured by flags:

• make two existing flags public:
  • --cache value Megabytes of memory allocated to internal caching (default: 1024)
  • --cache.database value Percentage of cache memory allowance to use for database io (default: 75)
• create a new flag:
  • --fdlimit value Raise the open file descriptor resource limit (default = system fd limit) (default: 0)

And apply below PRs:

• cmd: cap cache size if exceeds reasonable range ethereum/go-ethereum#16800
• common/fdlimit: cap on MacOS file limits, fixes #18994 ethereum/go-ethereum#19035
• common/fdlimit: fix windows build ethereum/go-ethereum#19068
• common/fdlimit: Fix compilation error in freebsd, Raise returns uint64 ethereum/go-ethereum#19141
• Upgrade to Go 1.12 ethereum/go-ethereum#19166
• common/fdlimit: build on DragonflyBSD ethereum/go-ethereum#21241
• Allow file descriptor limit to be set via CLI ethereum/go-ethereum#24477
• fix: linter warning ethereum/go-ethereum#25192
• cmd/geth: move cache sanity check to SetEthConfig ethereum/go-ethereum#22510

Types of changes

What types of changes does your code introduce to XDC network?
Put an ✅ in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)
• Regular KTLO or any of the maintaince work. e.g code style
• CICD Improvement

Impacted Components

Which part of the codebase this PR will touch base on,

Put an ✅ in the boxes that apply

• Consensus
• Account
• Network
• Geth
• Smart Contract
• External components
• Not sure (Please specify below)

Checklist

Put an ✅ in the boxes once you have confirmed below actions (or provide reasons on not doing so) that

• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
• N/A