Changes since 0.9.6

[tariqkurd-repo]

Encoding formats:

1. Rename encoding formats: Draft of _L<params> for capability encodings #845
2. Add CHERIoT Encoding formats: First draft of CHERIoT encoding chapters. #858

Extensions:

1. Separate YBLD into its own extension: push YBLD into Zyb #853
2. Vector integration marked as stable and integrated with main spec: enable vector for v1 ratification #860
3. Added extension for accessor instruction for capability top (from CHERIoT): YTOPR #868
4. Added extension for rounding-down version of YBNDSRW (from CHERIoT): Zybndsrd #870

CSRs:

1. Remove xycfg pending a general RISC-V discovery mechanism: put ifdefs around Xycfg #852 (it was only introduced in 0.9.5 to solve discovery, so no change from 0.9.4)
2. Add sstatus.UCRGE to enable Svucrg as otherwise the CRW=1, CD=0, UCRG=0 state is different depending on whether Svucrg is implemented or not, and can't be distinguished between. Add Svucrg enable bit. #867

Clarifications:

1. Allow tag clearing by the platform in LY, as Svucrg or CHERIoT's load filter can clear loaded tags - or the tag strip PMA of course allow revocation tag clearing in LY defn #865
2. Fix integrity check behaviour in YMODEW fix YMODEW to have full integrity checks #878
3. clarify reset values Clarify reset values for CSRs, in line with priv spec #883