[FIX] component, fiber: error_handling at the Fiber level

Before this commit, errors triggered at the level of the fiber (as opposed to at the level
of a component's rendering), were handled as the very top level of the rendering, that is,
in the scheduler.
This was wrong because components below in the rendering tree would not have a chance to handle their
children's or their own errors.

After this commit, error triggered in willPatch, onMounted and onPatched are correctly handled
at the closest component to where they were thrown.

tests/components/__snapshots__/error_handling.test.ts.snap

@@ -369,6 +369,116 @@ exports[`can catch errors can catch an error in the initial call of a component
 }"
 `;
 
+exports[`can catch errors can catch an error in the mounted call 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber, safeOutput } = helpers;
+  
+  let block1 = createBlock(\`<div>Some text</div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    return block1();
+  }
+}"
+`;
+
+exports[`can catch errors can catch an error in the mounted call 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber, safeOutput } = helpers;
+  
+  let block1 = createBlock(\`<div><block-child-0/><block-child-1/><block-child-1/></div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let b2,b3;
+    if (ctx['state'].error) {
+      b2 = text(\`Error handled\`);
+    } else {
+      b3 = callSlot(ctx, node, key, 'default');
+    }
+    return block1([], [b2, b3]);
+  }
+}"
+`;
+
+exports[`can catch errors can catch an error in the mounted call 3`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber, safeOutput } = helpers;
+  let assign = Object.assign;
+  
+  let block1 = createBlock(\`<div><block-child-0/></div>\`);
+  
+  const slot2 = ctx => (node, key) => {
+    return component(\`ErrorComponent\`, {}, key + \`__3\`, node, ctx);
+  }
+  
+  return function template(ctx, node, key = \\"\\") {
+    let b3 = assign(component(\`ErrorBoundary\`, {}, key + \`__1\`, node, ctx), {slots: {'default': slot2(ctx)}});
+    return block1([], [b3]);
+  }
+}"
+`;
+
+exports[`can catch errors can catch an error in the willPatch call 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber, safeOutput } = helpers;
+  
+  let block1 = createBlock(\`<div><block-text-0/></div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let d1 = ctx['props'].message;
+    return block1([d1]);
+  }
+}"
+`;
+
+exports[`can catch errors can catch an error in the willPatch call 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber, safeOutput } = helpers;
+  
+  let block1 = createBlock(\`<div><block-child-0/><block-child-1/><block-child-1/></div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let b2,b3;
+    if (ctx['state'].error) {
+      b2 = text(\`Error handled\`);
+    } else {
+      b3 = callSlot(ctx, node, key, 'default');
+    }
+    return block1([], [b2, b3]);
+  }
+}"
+`;
+
+exports[`can catch errors can catch an error in the willPatch call 3`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber, safeOutput } = helpers;
+  let assign = Object.assign;
+  
+  let block1 = createBlock(\`<div><span><block-text-0/></span><block-child-0/></div>\`);
+  
+  const slot2 = ctx => (node, key) => {
+    return component(\`ErrorComponent\`, {message: ctx['state'].message}, key + \`__3\`, node, ctx);
+  }
+  
+  return function template(ctx, node, key = \\"\\") {
+    let d1 = ctx['state'].message;
+    let b3 = assign(component(\`ErrorBoundary\`, {}, key + \`__1\`, node, ctx), {slots: {'default': slot2(ctx)}});
+    return block1([d1], [b3]);
+  }
+}"
+`;
+
 exports[`can catch errors can catch an error in the willStart call 1`] = `
 "function anonymous(bdom, helpers
 ) {