chore(frontends/lean): use consistent name conventions, rename token_set to token_table

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean/parse_table): add use_lambda_abstraction flag to scoped_expr_actions

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/aliases): add support for alias overloading

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean): add parser_config environment extension

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(frontends/lean/scanner): use the parser configuration in the environment

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean): add parser interface

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean): add parser interface