[bazel] Remove now-unused vendored Rust crate build files #3516

Job	Run time
Lint (quick)	3m 28s
Airgapped build	10m 19s
Run OTBN smoke Test	2m 58s
Run OTBN crypto tests	21m 53s
Build documentation	4m 47s
Lint (slow)	15m 16s
Verible lint	1m 7s
Verilated English Breakfast	8m 0s
Build Docker Containers	2m 42s
CW305's Bitstream	22m 49s
Build and test software	18m 26s
Verilated Earl Grey	1h 23m 23s
Earl Grey for CW310 / Build bitstream	1h 7m 58s
Earl Grey for CW310 Hyperdebug / Build bitstream	1h 14m 43s
Earl Grey for CW340 / Build bitstream	1h 28m 43s
CW310 Test ROM Tests / FPGA test	5m 34s
CW310 ROM_EXT Tests / FPGA test	6m 53s
CW310 ROM Tests / FPGA test	40m 2s
CW310 SiVal Tests / FPGA test	24m 50s
CW310 Manufacturing Tests / FPGA test	29m 7s
CW310 SiVal ROM_EXT Tests / FPGA test	34m 37s
Cache bitstreams to GCP	0s
CW340 ROM_EXT Tests / FPGA test	6m 15s
CW340 Manufacturing Tests / FPGA test	7m 26s
CW340 ROM Tests / FPGA test	52s
CW340 Test ROM Tests / FPGA test	4m 3s
CW340 SiVal ROM_EXT Tests / FPGA test	4m 55s
CW340 SiVal Tests / FPGA test	16m 11s
Verify FPGA jobs	38s
	10h 7m 55s

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