Currently, the `candid` crate mainly consists of two parts:
* Candid data encoding/decoding
* Parser and derived functionality (bindgen)

The second part evolves fast which forces us to bump major version frequently.
Such version bumps propagated to the downstream projects (agent-rs, cdk-rs, sdk, ic monorepo, etc).

By splitting out `candid_parser`, we expect to have a stable `candid` crate.

Also, I move `Principal` into a separate `ic_principal` crate. Therefore, we can provide a lightweight dependency for those who only need `Principal`.

## Notable changes
* Some private or crate public methods are now public since they are called cross-crate
* Add `parse_idl_args()` and `parse_idl_value()` because in `candid_parser` we cannot implement `FromStr` for `IDLArgs` and `IDLValue` which are defined in `candid`.
* `TypeEnv` is defined in `candid`, so we can't implement type method `ast_to_type` in `candid_parser`. Instead I turned it into a function which takes `TypeEnv` as the first argument. Similarly, `size_helper()` and `size()` are changed.

* remove num_enum

* clean up parser dependencies

* checkpoint

* value feature

* remove codespan

* fix

* fix

* pretty

* remove mute_warning

* fix

* pretty refactor

* fix

* reexport candid in parser

* fix

* fix

* fix

* bignum feature

* bump candid_derive

* silence subtyping in decoder

* fix service_equal error reporting (#486)

* add IDLValue::Blob

* builder for config

* fix

* fix

* fix service_equal error reporting (#486)

* Add Arbitrary for Principal and extend random for Func

* Use  instead of

* fmt

* add arbitrary for principal

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Co-authored-by: Yan Chen <[email protected]>