Fix(snowflake)!: refactor colon (extract) parsing precedence

[georgesittas]

We used to have mutual recursion between _parse_column_ops and _parse_colon_as_variant_extract, which resulted in a couple of issues:

1. The added test failed because there's a stack frame where the start-end token range represents the text 'level1 : level2: level3'. This resulted in a JSONPathKey that included the redundant whitespace following level1.
2. The recursion would lead to a complexity class of O(n²), involving various costly steps like parsing JSON paths and various function calls. This becomes an issue for queries with deeply nested JSON constructs where : is used to access the corresponding fields.

[github-actions]

SQLGlot Integration Test Results

Comparing:

• this branch (sqlglot:jo/fix_edge_case_sf_colon, sqlglot version: jo/fix_edge_case_sf_colon)
• baseline (main, sqlglot version: 28.10.1.dev68)

⚠️ Limited to dialects: snowflake

By Dialect

dialect	main	sqlglot:jo/fix_edge_case_sf_colon	transitions	links
snowflake -> duckdb	1529/2403 passed (63.6%)	1531/2403 passed (63.7%)	2 fail->pass	full result / delta
snowflake -> snowflake	2616/2623 passed (99.7%)	2616/2623 passed (99.7%)	No change	full result / delta

Overall

main: 5026 total, 4145 passed (pass rate: 82.5%), sqlglot version: 28.10.1.dev68

sqlglot:jo/fix_edge_case_sf_colon: 5026 total, 4147 passed (pass rate: 82.5%), sqlglot version: jo/fix_edge_case_sf_colon

Transitions: 2 fail->pass