chore: gh action caching for docker build layers

[zone117x]

Enable github action caching for build layers. Minor changes to Dockerfile to cache the apk add ... and npm install ... steps.

Should bring image build time down from minutes to tens of seconds.

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[codecov-commenter]

Codecov Report

Merging #901 (09810b4) into develop (fdbc548) will increase coverage by 0.57%. The diff coverage is 88.31%.

@@             Coverage Diff             @@
##           develop     #901      +/-   ##
===========================================
+ Coverage    66.01%   66.58%   +0.57%     
===========================================
  Files           92       95       +3     
  Lines         9856     9979     +123     
  Branches      1546     1564      +18     
===========================================
+ Hits          6506     6645     +139     
+ Misses        3346     3330      -16     
  Partials         4        4              

Impacted Files	Coverage Δ
src/api/routes/debug.ts	22.55% <0.00%> (ø)
src/datastore/common.ts	82.29% <ø> (ø)
src/datastore/memory-store.ts	6.98% <0.00%> (-0.05%)	:arrow_down:
src/api/routes/block.ts	75.67% <70.96%> (+2.79%)	:arrow_up:
src/api/init.ts	82.10% <75.00%> (-0.32%)	:arrow_down:
src/api/routes/tx.ts	74.69% <87.50%> (+0.75%)	:arrow_up:
src/api/async-handler.ts	88.88% <88.88%> (ø)
src/api/routes/core-node-rpc-proxy.ts	79.43% <88.88%> (-0.43%)	:arrow_down:
src/api/controllers/db-controller.ts	77.72% <90.62%> (+2.49%)	:arrow_up:
src/datastore/postgres-store.ts	83.65% <96.29%> (+0.25%)	:arrow_up:
... and 11 more

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[zone117x]

Hmm this isn't working as intended. None of the following steps are being cached:

RUN apk add --no-cache --virtual .build-deps alpine-sdk python3 git openjdk8-jre cmake
COPY package.json package-lock.json ./
RUN npm config set unsafe-perm true && npm install

Not really sure why not, probably something weird with the docker context being detected as changed. I'll wait for @CharlieC3 to possibly provide some insight.

[zone117x]

Closing this PR for now. I opened an issue to track if we want to work on it in the future: https://github.com/hirosystems/stacks-blockchain-api/issues/1623