CI: Split the RISC-V Build Jobs into smaller jobs

[lupyuen]

Summary

To speed up the CI Workflow, this PR splits the CI Build Jobs for RISC-V into smaller jobs. Each job will now complete within 1 hour.

Before the PR: There are 2 jobs for RISC-V, each requiring more than 1.5 hours

• risc-v-01 (1 hour 42 mins): BL602, Ox64, ESP32-C3 / C6 / H2
• risc-v-02 (1 hour 41 mins): K230, Icicle, QEMU, RV32M1-Vega

After the PR: The build is spread across 6 jobs for RISC-V, each job completes within 1 hour

• risc-v-01 (19 mins): BL602, Ox64
• risc-v-02 (44 mins): ESP32-C3
• risc-v-03 (45 mins): ESP32-C6, ESP32-H2
• risc-v-04 (31 mins): K230, Icicle
• risc-v-05 (41 mins): QEMU CITest
• risc-v-06 (38 mins): Rest of QEMU, RV32M1-Vega

Following the same convention as the Arm32 Build Jobs, the above jobs are sorted by Target Name. Performance of the RISC-V Build Jobs is discussed in apache#13775

Impact

With this PR, RISC-V Build Jobs will finish earlier:

Before the PR: RISC-V Build Jobs take up to 1 hour 42 mins (risc-v-01) to complete.

After the PR: RISC-V Build Jobs will take at most 45 mins (risc-v-03) to complete.

The Updated CI Workflow shall be synced to nuttx-apps repo in the next PR.

Testing

We verified that RISC-V Build Jobs are executed successfully with the Updated CI Workflow: https://github.com/lupyuen5/label-nuttx/actions/runs/11255875050

Timings for the RISC-V Build Jobs:

Before the PR

• risc-v-01: 1 hour 42 mins
• risc-v-02: 1 hour 41 mins

After the PR

• risc-v-01: 19 mins
• risc-v-02: 44 mins
• risc-v-03: 45 mins
• risc-v-04: 31 mins
• risc-v-05: 41 mins
• risc-v-06: 38 mins