handlebar defaultContext support for build-contexts input #2003

Job	Run time
example	23s
git-context	21s
git-context-secret	27s
minimal	23s
path-context	16s
docker-driver	15s
error	5s
error-buildx	28s
export-docker	11s
network	16s
secret	23s
secret-envs	14s
shm-size	19s
add-hosts	14s
ulimit	27s
cgroup-parent	29s
attests-compat (latest, moby/buildkit:buildx-stable-1)	34s
multi (multi)	33s
digest (docker, true, false)	22s
attests-compat (latest, moby/buildkit:v0.10.6)	36s
multi (multi-sudo)	33s
digest (docker, false, true)	24s
attests-compat (v0.9.1, moby/buildkit:buildx-stable-1)	27s
no-cache-filters	17s
digest (docker, false, false)	22s
digest (docker-container, true, false)	20s
sbom (image, type=image,name=localhost:5000/name/app:latest,push=true)	33s
provenance (image, type=image,name=localhost:5000/name/app:latest,push=true, mode=max)	40s
annotations	19s
digest (docker-container, false, true)	25s
sbom (binary, /tmp/buildx-build)	25s
provenance (image, type=image,name=localhost:5000/name/app:latest,push=true)	29s
digest (docker-container, false, false)	21s
provenance (binary, /tmp/buildx-build, mode=max)	30s
docker-config-malformed	15s
github-cache	17s
provenance (binary, /tmp/buildx-build)	38s
load-and-push	20s
local-cache	25s
multi-output	25s
named-context-container	38s
named-context-docker	22s
named-context-pin	14s
proxy-buildkitd	21s
proxy-docker-config	26s
registry-cache	25s
standalone	14s
annotations-disabled	13s
call-check	12s
checks (latest)	14s
record-retention-days (2)	16s
record-upload-disable	17s
checks (v0.14.1)	13s
record-retention-days (0)	16s
summary-disable	20s
summary-disable-deprecated	22s
summary-not-supported	20s
	21m 4s

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