Release 0.12.3

What's Changed

• feat(client): add get_block_infos and deprecate get_blocks by @luisschwab in #164
• chore: use the alloc feature on serde_json by @luisschwab in #168
• Update broken pins for 1.63.0 MSRV by @luisschwab in #170
• chore(release): bump package to 0.12.3 by @luisschwab in #167
• [0.12.x] Fix pinning for MSRV and introduce ci/pin-msrv.sh script by @luisschwab in #173

Full Changelog: v0.12.2...v0.12.3