Enables request auto-refresh behaviors

This PR

• Test: if no cancelled block is present, abort may be handled by error block
• Test: if no error block is present, non-abort-error is rethrown
• Test: if no error block is present, abort-error is not-rethrown
• Impl: if no error block is present, abort-error is not-rethrown
• Impl: cancelled block exposes state with retry function
• Impl: error block exposes state with retry function
• Test: cancelled block exposes state with retry function
• Test: error block exposes state with retry function
• Impl: @Autorefresh enables automatic refresh after background resume
• Impl: @autorefreshThreshold enables configuration of amount of time in background required before autorefresh will be attempted on resume
• Impl: @autorefreshBehavior allows 'refresh' 'reload' and 'policy'
• Test: @Autorefresh enables automatic refresh after background resume
• Test: @autorefreshThreshold enables configuration of amount of time in background required before autorefresh will be attempted on resume
• Test: @autorefreshBehavior allows 'reload'
• Impl: content block exposes state with refresh function
• Impl: content block exposes state with reload function
• Impl: content block exposes state with isRefreshing property
• Impl: content block exposes state with abort function when isRefreshing is true
• Impl: content block exposes state with latestRequest

Under Consideration / Future PR

• Test: content block exposes state with refresh function
• Test: content block exposes state with reload function
• Test: content block exposes state with isRefreshing property
• Test: content block exposes state with abort function when isRefreshing is true
• Test: content block exposes state with latestRequest
• Test: @autorefreshBehavior allows 'refresh'
• Test: @autorefreshBehavior allows 'policy'
• Test/Impl: request subscribes to external updates to the request as background updates
• Test/Impl: multiple request components dedupe their autorefresh behavior