Suppress debug-level SDK logs in tests

[mark-rushakoff]

There are many SDK logs with level=DEBUG that are usually not interesting to us in gcosmos tests:

    logger.go:257: time=2024-10-30T20:08:34.684Z level=DEBUG msg="running initialization for module" val_idx=0 module=consensus
    logger.go:257: time=2024-10-30T20:08:34.684Z level=DEBUG msg="running initialization for module" val_idx=0 module=accounts
...
    logger.go:257: time=2024-10-30T20:08:34.712Z level=DEBUG msg=recursiveRemove val_idx=0 node="Node{1:\n@ <nil>:- 1-0 }#\n" key="C\x00\x00\x00\x00\x00\x00\x00\x1d1970-01-01T00:00:00.000000000\x00\x00\x00\x00\x00\x00\x00\x00"
...
    logger.go:257: time=2024-10-30T20:08:34.720Z level=DEBUG msg="BATCH SAVE" val_idx=0 node="Node{\x06:@ (1, 1):000000000000000100000002-000000000000000100000009 7-3 83f6aa9b551fb61d24a9e047ada4be5e6a9f0968a23f72ffe2ffaee700dd13e1}#{left (1, 2)}{right (1, 9)}\n"
    logger.go:257: time=2024-10-30T20:08:34.720Z level=DEBUG msg="SAVE TREE" val_idx=0 version=1

The gcosmos tests call gcosmos/internal/copy/gtest.NewTestLogger to produce the test logger:

gcosmos/internal/copy/gtest/log.go

Lines 10 to 17 in fde677d

	// NewLogger returns a *slog.Logger associated with the test t.
	func NewLogger(t testing.TB) *slog.Logger {
	// The slogt package has been stable and effective
	// for adapting slog to testing.T.Log calls.
	// Prefer to abstract slogt behind a gtest interface
	// to reduce a direct dependency from tests to an external module.
	return slogt.New(t, slogt.Text())
	}

Change that plain call to slogt.New to use slogt.Bridge. Continue to use the Text handler, but set the Bridge's Handle method to drop records that have level debug and that do not have root=gcosmos, so that we can still see gcosmos debug logs by default.