fix: txtar tests load full config and execute serially #1427

Job	Run time
build (1.20.x, amd64, linux, ./pkg/amino/cmd/aminoscan)	6s
build (1.20.x, amd64, linux, ./pkg/amino/cmd/goscan)	27s
test (1.20.x, _test.flappy)	24s
build (1.20.x, amd64, linux, ./pkg/autofile/cmd)	11s
test (1.20.x, _test.pkg.amino)	5m 0s
build (1.20.x, amd64, linux, ./pkg/iavl/cmd/iaviewer)	15s
test (1.20.x, _test.pkg.bft)	4m 49s
build (1.21.x, amd64, linux, ./pkg/amino/cmd/aminoscan)	9s
test (1.20.x, _test.pkg.others)	6m 39s
build (1.21.x, amd64, linux, ./pkg/amino/cmd/goscan)	8s
test (1.21.x, _test.flappy)	24s
build (1.21.x, amd64, linux, ./pkg/autofile/cmd)	14s
test (1.21.x, _test.pkg.amino)	3m 36s
build (1.21.x, amd64, linux, ./pkg/iavl/cmd/iaviewer)	10s
test (1.21.x, _test.pkg.bft)	4m 31s
test (1.21.x, _test.pkg.others)	3m 44s
upload-coverage	9s
	30m 56s

Provide feedback