Changes

• Add a parameter 'stakable' in getBlobbers wasm API to list only blobbers that can be staked.
• Provide additional function parameter in GetValidators(), GetMiners() and GetSharders() to list only validators, miners and sharders that can be staked respectively .

Fixes

Tests

Tasks to complete before merging PR:

• Ensure system tests are passing. If not Run them manually to check for any regressions 📋
• Do any new system tests need added to test this change? do any existing system tests need updated? If so create a PR at 0chain/system_test
• Merge your system tests PR to master AFTER merging this PR

Associated PRs (Link as appropriate):

• blobber:
• 0chain:
• system_test:
• zboxcli:
• zwalletcli:
• Other: ...