Yul identifiers inconsistently treat builtins/keywords

For example, [yul-variable-declaration](https://docs.soliditylang.org/en/latest/grammar.html#a4.SolidityParser.yulVariableDeclaration) specifies one or more yul-identifiers on the left hand side; yul-identifier is a separate rule from yul-evm-builtin, so I assume in practice this means that yul-identifier excludes all evm builtins. However, yul-path (part of yul-expression) specifies only yul-identifier as the first segment.

The following code is allowed:
```solidity
contract C {
uint number;
function f() external {
assembly {
// whereas declaring 'number' inside is not
// let number := 0
sstore(number.slot, 1)
}
}
}
```

I believe the implementation is correct, but the grammar is missing this nuance.

Encountered in Optimism: https://github.com/ethereum-optimism/optimism/blob/5229fa195415136e5589787c5850101d06b15748/packages/contracts-bedrock/src/L2/L1Block.sol#L169-L170

The report names yul-variable-declaration, yul-identifier, yul-evm-builtin, and yul-path, with an example in Optimism's L1Block.sol. Start by comparing these grammar rules with the implementation; done when the grammar consistently documents how builtins and keywords are treated.

Written by the indexing model from the issue text.