fix(athena): properly escape identifiers in Iceberg SQL generation

[kukushking]

Description

Column and table identifiers are interpolated into the SQL that the Iceberg
write path generates (awswrangler/athena/_write_iceberg.py) without escaping.
Names containing the quoting character aren't quoted correctly, which produces
malformed SQL or unexpected behavior for identifiers that contain special
characters.

This can surface without any unusual caller input. During automatic schema
reconciliation (to_iceberg(..., fill_missing_columns_in_df=True), the
default), column names are read back from the AWS Glue Data Catalog and then
interpolated into the generated MERGE/INSERT. Glue permits identifiers that
the generation didn't handle safely, so this hardens the path against names
sourced from the catalog rather than only from the DataFrame.

Changes

Athena uses two identifier-quoting families depending on the statement:
Hive-style backticks for DDL (CREATE TABLE, ALTER TABLE) and Trino-style
double quotes for DML (SELECT/INSERT/MERGE/DELETE). This PR adds a
helper for each and applies it consistently:

• _escape_athena_identifier() — doubles embedded ", for DML identifiers.
• _escape_athena_ddl_identifier() — doubles embedded `, for DDL identifiers.

Applied to every identifier splice in the module:

• DML: _merge_iceberg (MERGE/INSERT), delete_from_iceberg_table, and the
  mode="overwrite" DELETE FROM.
• DDL: _create_iceberg_table (table + column names), _alter_iceberg_table_add_columns_sql,
  _alter_iceberg_table_change_columns_sql.
• _build_order_by_clause column identifiers.
• Routed the LOCATION '<path>' splice through the existing string-literal escaper.

Left unchanged on purpose: partition_cols are partition transform
expressions (e.g. day(ts), truncate(10, col)), not plain identifiers, so
they are spliced verbatim rather than quoted.

Testing

• Added unit tests for both helpers and each call site, using identifiers that
  contain the relevant quote character.
• ruff format --check, ruff check, and mypy clean on the changed files.

[EthanBunce]

Looks good to me