build(toolchain): bump to nightly-2023-10-21

[TennyZhuang]

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What's changed and what's your intention?

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

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Release note

If this PR includes changes that directly affect users or other significant modifications relevant to the community, kindly draft a release note to provide a concise summary of these changes. Please prioritize highlighting the impact these changes will have on users.

[BugenZhao]

Cool

[xxchan]

Shoud change no_coverage to coverage(off) rust-lang/rust#84605

[TennyZhuang]

Currently blocked on sgodwincs/dlv-list-rs#19 (comment)

[codecov]

Codecov Report

Merging #12992 (1000000) into main (210ae71) will increase coverage by 0.06%.
The diff coverage is 16.66%.

@@            Coverage Diff             @@
##             main   #12992      +/-   ##
==========================================
+ Coverage   68.63%   68.70%   +0.06%     
==========================================
  Files        1495     1495              
  Lines      251192   251161      -31     
==========================================
+ Hits       172401   172551     +150     
+ Misses      78791    78610     -181     

Flag	Coverage Δ
rust	68.70% <16.66%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/batch/src/rpc/service/task_service.rs	0.00% <ø> (ø)
src/cmd/src/lib.rs	0.00% <ø> (ø)
src/cmd_all/src/bin/risingwave.rs	0.00% <ø> (ø)
src/common/proc_macro/src/config.rs	81.81% <ø> (ø)
src/common/proc_macro/src/lib.rs	74.50% <ø> (ø)
src/common/src/types/ordered.rs	80.95% <ø> (ø)
src/compute/src/lib.rs	17.50% <ø> (ø)
src/compute/src/rpc/service/exchange_service.rs	0.00% <ø> (ø)
src/compute/src/rpc/service/monitor_service.rs	0.00% <ø> (ø)
src/compute/src/rpc/service/stream_service.rs	0.00% <ø> (ø)
... and 27 more

... and 83 files with indirect coverage changes

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[TennyZhuang]

Currently blocked on sgodwincs/dlv-list-rs#19 (comment)

Now it's here. zonyitoo/rust-ini#115 (comment)