Pallet grouping macros

[4meta5]

Implements wrapper macros for all pallet groupings

PR using macros in both runtime templates

• closes System grouping #3
• closes Consensus grouping #10
• closes Governance grouping #13
• closes Xcm grouping #14
• closes Asset grouping #11
• closes EVM grouping #12

Final TODOs:

• in-line docs per grouping (thanks @ggonzalez94 )
• closes Showcase the API on readme.md #5 (done in 640268e 07ce4fb)

Tanssi fixes:

• move pallet-sessions to consensus grouping from system grouping
• expose ProxyType in the system grouping

Patches merged into macros that should be reviewed closely:

• xtokens config polkadot-runtime-templates#331
• xtokens on generic polkadot-runtime-templates#343
• xcm-transactor on evm polkadot-runtime-templates#345
• xcm-transactor on generic polkadot-runtime-templates#346
• #305 Fixing unexpectedly high weights for XCM pallet polkadot-runtime-templates#322
• use asset hub as reserve polkadot-runtime-templates#327
• merge changes/fixes from v2 back into main polkadot-runtime-templates#333
• Generic asset manager polkadot-runtime-templates#341

Follow ups

• Expose to set all config types that lack local def  #8
• Clean code comments in macro expansion (from templates) #24
• Expose governance tracks #25
• Expose WeightInfos #26
• Expose all xcm fee types #27
• Expose all Get<Balance> types #28
• Allow EVM parachains to configure gas settings #29

[4meta5]

Scope for this PR is closed and #8 is clearly a follow up. Going forward I would appreciate a constructive review that actually checks that all the patches were properly included.

[4meta5]

The remaining work that needs to be focused on in this PR is adding xtokens and xcm-transactor. We need to focus on these changes before anything else.

[ggonzalez94]

Left a few nits and suggestions, especially around comments and how we document the macro. I think:

• We should step up our game in terms of in-line docs, each grouping should have an explanation of what it does and what pallets it uses(I tried to provide an example for assets)
• I saw a lot of inconsistencies in comments(/// and //), these were probably porter over from the templates repo, but I think it is a good opportunity to fix them.

[4meta5]

@ggonzalez94 I did not add any comments to the code, these all existed in our templates. Let's address code comments inside the expansion in a follow up so that I can focus on merging in all of the work that has been only merged into the templates today. #24

[4meta5]

Currently updating templates PR to use the most recent commit (OpenZeppelin/polkadot-runtime-templates#300 (comment)). Need to validate the last commit works for both templates before merging.

[4meta5]

Both templates are compiling with the latest macros commit, see OpenZeppelin/polkadot-runtime-templates#300 (comment)

[4meta5]

Still updating in-line docs and the README in this PR to follow review suggestions

[4meta5]

Need to re-review xtokens, xcm-weight-trader, and xcm-transactor configurations in templates tomorrow with fresh eyes before final merge

[ggonzalez94]

Looks good! Left some suggestions for the module comments, feel free to take them if you didn't work on them already

[4meta5]

This PR is ready to be merged, but I am not completely satisfied with the README. One point of confusion right now is that the repository is polkadot-runtime-wrappers and the crate name is openzeppelin-polkadot-wrappers. This comes up a few times and I think it would be more clear if the repository was renamed to match the crate name. @ggonzalez94 let me know what you think and maybe we can create a follow up issue to rename the repo and update the README to clear any confusion around this