RISC-V Vector Extension Support

This PR adds the following:

General Framework and Configurations:

* Introduced the V extension's general framework and configuration setting instructions.
* Updated model/riscv_insts_vext_vset.sail and effect matching functions in riscv_vlen.sail.
* Addressed code formatting issues and made revisions post the Nov 22 meeting.
* Co-authored by Nicolas Brunie and Jessica Clarke.

Vector Load/Store Instructions:

* Integrated vector load and store instructions.
* Enhanced the implementation of SEW, LMUL, VLEN and removed real numbers from the code.
* Updated vstart settings and removed unnecessary assert statements.
* Rectified bugs in vleff instructions and overhauled coding styles.
* Incorporated guards for vector encdec clauses and optimized memory access post vector load/store failures.

Vector Integer/Fixed-Point Instructions:

* Added vector integer/fixed-point arithmetic and mask instructions.
* Improved vector EEW and EMUL checking functions and introduced illegal instruction check functions.
* Fine-tuned code formatting for vector instruction checks.

Vector Floating-Point Instructions:

* Rolled out vector floating-point instructions and updated their conversion counterparts.
* Refreshed copyright headers specific to the vector extension code.

Vector Reduction and Mask Instructions:

* Integrated vector mask and reduction instructions.
* Addressed register overlap checks for vector mask instructions.

Miscellaneous Enhancements and Fixes:

* Updated vector CSR vtype.vill settings and judgements.
* Systematized patterns for vector illegal instruction checks.
* Rectified issues in vector load/store and reduction operations.
* Purged redundant elements from the V extension code and vector floating-point functions.
* Cleaned up softfloat makefiles and renamed EXTZ and EXTS within the V extension code.
* Addressed a clang-format check issue and NaN boxing anomalies. Provided annotations for pending RVV configurations.
* Initialized default VLEN value and set vlenb CSR.
* Set constraints for vector variable initialization and added mstatus.VS settings specific to the vector extension.