feat: verify insertMany method for adding lists to HashMaps

[monsterkrampe]

This PR verifies the insertMany method on HashMaps for the special case of inserting lists.

[leanprover-community-bot]

Mathlib CI status (docs):

• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase 935fcfb6ec84342163a86058856edcb1dca70ff4 --onto 884a9ea2ff70bb4d0c6da4a1c23ffc26c3a974ee. (2024-11-25 13:30:54)
• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase 0a22f8fa6fef34a6798785785237c66cab173197 --onto 9a17919ef11c2dba824498229633b8333a0b53d9. (2024-11-26 15:53:38)
• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase b378fe98a7877276b7dff70527b6c924e672c435 --onto 9a17919ef11c2dba824498229633b8333a0b53d9. (2024-11-27 15:47:35)
• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase b378fe98a7877276b7dff70527b6c924e672c435 --onto 609346f5e03f3f2d559e7cc905f72e950c3ed8c4. (2024-11-28 08:49:25)
• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase b378fe98a7877276b7dff70527b6c924e672c435 --onto 6d495586a1836da3e12efb4fbf9946bd9088ac5f. (2024-11-29 10:41:50)