chore: release v0.21.0

[github-actions]

🤖 New release

• salsa-macro-rules: 0.20.0 -> 0.21.0
• salsa-macros: 0.20.0 -> 0.21.0
• salsa: 0.20.0 -> 0.21.0 (⚠ API breaking changes)

⚠ salsa breaking changes

--- failure enum_struct_variant_field_added: pub enum struct variant field added ---

Description:
An enum's exhaustive struct variant has a new field, which has to be included when constructing or matching on this variant.
        ref: https://doc.rust-lang.org/reference/attributes/type_system.html#the-non_exhaustive-attribute
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.40.0/src/lints/enum_struct_variant_field_added.ron

Failed in:
  field key of variant EventKind::DidInternValue in /tmp/.tmpDzBO14/salsa/src/event.rs:105
  field key of variant EventKind::DidReinternValue in /tmp/.tmpDzBO14/salsa/src/event.rs:114

--- failure enum_struct_variant_field_missing: pub enum struct variant's field removed or renamed ---

Description:
A publicly-visible enum has a struct variant whose field is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.40.0/src/lints/enum_struct_variant_field_missing.ron

Failed in:
  field id of variant EventKind::DidInternValue, previously in file /tmp/.tmpB9VUBN/salsa/src/event.rs:105
  field id of variant EventKind::DidReinternValue, previously in file /tmp/.tmpB9VUBN/salsa/src/event.rs:114

Changelog

salsa-macro-rules

0.20.0 - 2025-04-22

Added

• Drop Debug requirements and flip implementation defaults (#756)

Other

• Reduce memory usage by deduplicating type information (#803)
• Inline/Outline more cold and slow paths (#805)
• rewrite cycle handling to support fixed-point iteration (#603)

salsa-macros

0.21.0 - 2025-04-24

Other

• Use DatabaseKey for interned events (#813)

salsa

0.21.0 - 2025-04-24

Other

• Use DatabaseKey for interned events (#813)
• [refactor] More fetch_hot simplification (#793)
• Don't store the fields in the interned map (#812)
• Fix ci not always running (#810)

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