fix: use proper xid types for xpending range

[ArturSharapov]

A range that can be used in XPENDING is defined the same way as in XRANGE.

Currently, when calling xpendingCount the start and end arguments have number | "-" type, which prevents users from specifying other valid forms of XIdInput and indicates that the method cannot process an XId object.

Proposed changes

• Update type definitions of start and end to XIdNeg and XIdPos accordingly, just like it's done for xrange.
• Wrap start and end arguments with xidstr that would transform a valid xIdInput to string ID.

[uki00a]

LGTM! Thanks for the contribution!