Generate regular GRIB coordinates lazily

[michaeldiener]

Opening a GRIB file currently materializes its regular horizontal coordinate arrays, even when the caller only reads the weather field.
Generate these coordinates through a ProxyReader when requested, using normal variable caching behavior.
This applies to regular projected, latitude/longitude and rotated latitude/longitude axes; Gaussian latitude arrays stay on their existing path.

Section reads generate the requested indexes using the original start + index * increment expression.
This preserves the full-array values and rounding, including strided sections, without constructing the whole coordinate first for an uncached axis.
In a 349-field ICON workload that does not read these coordinates, this avoids 3.83 GiB of temporary array allocation.

Validation:

• Added tests for lazy file opening, exact full/strided values, positive and negative increments, sections of sections, slices, copied variables and mutation isolation for cached and uncached axes.
• The file-opening regression fails before the builder change and passes afterwards.
• All 349 real ICON fields retain identical raw float bits and shapes.
• The new tests pass on Java 8 and Java 21 on Linux, and Java 21 on macOS.
• Repository-wide spotlessCheck passes.
• GitHub Actions passes all build, documentation and style checks, plus the Java 8, 11, 17, 21 and 25 test matrix on both Temurin and Corretto.
• On macOS, the full enabled GRIB suite has 170 passing tests and 20 failures in the two existing S3 test classes.
  Those HTTP 301/400 failures also reproduce using unchanged upstream classes while opening the remote test objects.

[CLAassistant]

All committers have signed the CLA.

[lesserwhirls]

Thank you for this contribution! The trade-off between memory usage and CPU cycles seems well worth it.