feat: export the getCrc32 function from @dfinity/principal

[ilbertt]

Description

Moves all the content of the packages/principal/src/index.ts into packages/principal/src/principal.ts and re-export them from packages/principal/src/index.ts. Renames packages/principal/src/index.test.ts into packages/principal/src/principal.test.ts.

Exports the getCrc32 function as well.

How Has This Been Tested?

Same tests should still pass.

Checklist:

• My changes follow the guidelines in CONTRIBUTING.md.
• The title of this PR complies with Conventional Commits.
• I have edited the CHANGELOG accordingly.
• I have made corresponding changes to the documentation.

[github-actions]

size-limit report 📦

Path	Size
@dfinity/agent	47.86 KB (0%)
@dfinity/assets	52.84 KB (0%)
@dfinity/auth-client	19.38 KB (0%)
@dfinity/candid	13.22 KB (0%)
@icp-sdk/core	91 B (0%)
@dfinity/identity	18.81 KB (0%)
@dfinity/identity-secp256k1	33.03 KB (0%)
@dfinity/principal	4.44 KB (0%)
@dfinity/use-auth-client	58.75 KB (0%)