REST Catalog: Attempting to load a table with a reserved name (e.g., snapshots) before creation causes an error

### Apache Iceberg version

1.9.0 (latest release)

### Query engine

Spark

### Please describe the bug 🐞

# Description
When using the Spark engine with the REST Catalog, attempting to load a table that has a reserved name (e.g., metadata, snapshots, etc.) before creating it triggers an unexpected error. This behavior check for table existence before creation.

# Steps to Reproduce
just past this code in org.apache.iceberg.rest.TestRESTCatalog
```java
@Test
public void reproduceError(){
RESTCatalog catalog = catalog();
catalog.createNamespace(Namespace.of("newdb"));
TableIdentifier identifier = TableIdentifier.of("newdb", "snapshots");
if(catalog.tableExists(identifier)){
catalog.buildTable(identifier, SCHEMA).create();
}
catalog.loadTable(identifier);
}
```

# Expected Behavior
Loading a non-existent table should return false if the table does not exist.
Creating a table with a reserved name should success

# Actual Behavior
throw errors in `TableIdentifier identifier = TableIdentifier.of("newdb", "snapshots");`

### Willingness to contribute

- [x] I can contribute a fix for this bug independently
- [x] I would be willing to contribute a fix for this bug with guidance from the Iceberg community
- [ ] I cannot contribute a fix for this bug at this time

Start in org.apache.iceberg.rest.TestRESTCatalog and run the provided reproduction with a reserved table name such as snapshots. Trace RESTCatalog.tableExists, buildTable, and loadTable for that identifier, then add coverage showing the expected behavior for a non-existent reserved-name table and successful creation before running the REST catalog tests.

Written by the indexing model from the issue text.