CDRIVER-3755 Provide an index creation helper (#1303)

* format mongoc-collection.c

* add `mongoc_collection_create_indexes_with_opts`

* make `assert_match_bson` a macro

Includes the caller's file and line number on error.

* fixup `hex_to_bin` helper

- return NULL if `hex` is NULL
- set `len` to 0 on error

This fixes a possible crash if LOCAL_MASTERKEY is not set in the example.

* update legacy test runner to use `mongoc_collection_create_indexes_with_opts`

* use `mongoc_collection_create_indexes_with_opts` in `create_collection_with_encryptedFields`

* use `mongoc_collection_create_indexes_with_opts` in `operation_create_index`

* fix placement of `strlen`

`strlen` was called was before `to_encrypt.value.v_utf8.str` was assigned. This resulted in a `strlen` call with `NULL` argument.

* use `mongoc_collection_create_indexes_with_opts` in examples

* add documentation page for `mongoc_collection_create_indexes_with_opts`

* update "Creating Indexes" guide

* add file name to example error message

Co-authored-by: vector-of-bool <vectorofbool@gmail.com>

* fix documented type of `models` to include `*`

Co-authored-by: Ezra Chung <88335979+eramongodb@users.noreply.github.com>

* simplify error handling

Co-authored-by: Ezra Chung <88335979+eramongodb@users.noreply.github.com>

* revise assert message

Co-authored-by: Ezra Chung <88335979+eramongodb@users.noreply.github.com>

* use `mongoc_collection_create_indexes_with_opts` in more tests

* rename FAIL to HANDLE_ERROR

* document "success" and "failure" paths in example

* rename guide page to "Manage Collection Indexes"

* rename guide file to `manage-collection-indexes.rst`

* rename `example-create-indexes.c` to `example-manage-collection-indexes.c`

* add "See Also" sections

* link to `createIndexes` documentation for form of `keys`

* document `mongoc_index_model_t`

* change `BSON_ASSERT` to `return NULL;`

* make pointer argument const

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Co-authored-by: vector-of-bool <vectorofbool@gmail.com>
Co-authored-by: Ezra Chung <88335979+eramongodb@users.noreply.github.com>