Update to Automatic Bandwidth Adjustment Procedure of Stateful PCE for MPLS-TE and SR-TE LSPs

The Stateful PCE extensions allow Stateful control of Traffic Engineering (TE) LSPs using PCEP for RSVP-TE and Segment Routing (SR) (for both MPLS and IPv6 Data planes) for both PCE-Initiated and PCC- Initiated LSPs. Extensions to the Path Computation Element Communication Protocol (PCEP) for MPLS-TE Label Switched Path (LSP) Automatic Bandwidth Adjustments with Stateful PCE are defined in RFC 8733. It defines the AUTO-BANDWIDTH-ATTRIBUTES TLV and a set of sub-TLVs for each of the attributes. The sub-TLVs are included if there is a change since the last information sent in the PCEP message. However, it lacks a mechanism to remove an attribute identified by the sub-TLV explicitly. This document updates RFC 8733 by defining the behaviour to remove an attribute explicitly. In addition, this updates allow applying this PCEP extensions to SR-TE LSPs (for both MPLS and IPv6 Data planes), in addition to MPLS-TE LSPs.