[fleet] Remove unnecessary ghost colors from EuiBottomBar (#169310)

## Summary

👋 Hey y'all - EUI will shortly be deprecating the `ghost` color in all
button components (see
https://eui.elastic.co/v89.0.0/#/navigation/button#ghost-vs-dark-mode).

In this PR, all components using `color="ghost"` are being used within
an `EuiBottomBar` and as such already automatically inherit dark mode
coloring.

I'm opening this PR ahead of time for your team so you can test this
migration and ensure no UI regressions have occurred as a result.

### Checklist

- [x] Tested in light and dark mode

x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/create_package_policy_page/multi_page_layout/components/bottom_bar.tsx

@@ -55,7 +55,7 @@ export const CreatePackagePolicyBottomBar: React.FC<{
         <EuiFlexItem grow={false}>
           <EuiFlexItem grow={false}>
             {/* eslint-disable-next-line @elastic/eui/href-or-on-click */}
-            <EuiButtonEmpty color="ghost" size="s" href={cancelUrl} onClick={cancelClickHandler}>
+            <EuiButtonEmpty color="text" size="s" href={cancelUrl} onClick={cancelClickHandler}>
               {cancelMessage || (
                 <FormattedMessage
                   id="xpack.fleet.createPackagePolicyBottomBar.backButton"
@@ -102,7 +102,7 @@ export const AgentStandaloneBottomBar: React.FC<{
         <EuiFlexItem grow={false}>
           <EuiFlexItem grow={false}>
             {/* eslint-disable-next-line @elastic/eui/href-or-on-click */}
-            <EuiButtonEmpty color="ghost" size="s" href={cancelUrl} onClick={cancelClickHandler}>
+            <EuiButtonEmpty color="text" size="s" href={cancelUrl} onClick={cancelClickHandler}>
               <FormattedMessage
                 id="xpack.fleet.agentStandaloneBottomBar.backButton"
                 defaultMessage="Go back"
@@ -134,7 +134,7 @@ export const CreatePackagePolicyFinalBottomBar: React.FC<{
       <EuiFlexGroup justifyContent="spaceBetween" alignItems="center">
         <EuiFlexItem grow={false}>
           <EuiFlexItem grow={false}>
-            <EuiButtonEmpty color="ghost" size="s" href={getHref('integrations_all')}>
+            <EuiButtonEmpty color="text" size="s" href={getHref('integrations_all')}>
               <FormattedMessage
                 id="xpack.fleet.createPackagePolicyBottomBar.addAnotherIntegration"
                 defaultMessage="Add another integration"
@@ -193,7 +193,7 @@ export const AgentDataTimedOutBottomBar: React.FC<{
       <EuiFlexGroup justifyContent="spaceBetween" alignItems="center">
         <EuiFlexItem grow={false}>
           <EuiButtonEmpty
-            color="ghost"
+            color="text"
             size="s"
             href={troubleshootLink}
             iconType="popout"

x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/create_package_policy_page/single_page_layout/index.tsx

@@ -471,7 +471,7 @@ export const CreatePackagePolicySinglePage: CreatePackagePolicyParams = ({
                 <EuiFlexItem grow={false}>
                   {/* eslint-disable-next-line @elastic/eui/href-or-on-click */}
                   <EuiButtonEmpty
-                    color="ghost"
+                    color="text"
                     href={cancelUrl}
                     onClick={cancelClickHandler}
                     data-test-subj="createPackagePolicyCancelButton"
@@ -488,7 +488,7 @@ export const CreatePackagePolicySinglePage: CreatePackagePolicyParams = ({
                       request={devtoolRequest}
                       description={devtoolRequestDescription}
                       btnProps={{
-                        color: 'ghost',
+                        color: 'text',
                       }}
                     />
                   </EuiFlexItem>

x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/details_page/components/settings/index.tsx

@@ -187,7 +187,7 @@ export const SettingsView = memo<{ agentPolicy: AgentPolicy }>(
                   <EuiFlexGroup gutterSize="s" justifyContent="flexEnd">
                     <EuiFlexItem grow={false}>
                       <EuiButtonEmpty
-                        color="ghost"
+                        color="text"
                         onClick={() => {
                           setAgentPolicy({ ...originalAgentPolicy });
                           setHasChanges(false);
@@ -204,7 +204,7 @@ export const SettingsView = memo<{ agentPolicy: AgentPolicy }>(
                         <DevtoolsRequestFlyoutButton
                           isDisabled={isLoading || Object.keys(validation).length > 0}
                           btnProps={{
-                            color: 'ghost',
+                            color: 'text',
                           }}
                           description={i18n.translate(
                             'xpack.fleet.editAgentPolicy.devtoolsRequestDescription',

x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/edit_package_policy_page/index.tsx

@@ -439,7 +439,7 @@ export const EditPackagePolicyForm = memo<{
                 <EuiFlexItem grow={false}>
                   <EuiFlexGroup gutterSize="s" justifyContent="flexEnd">
                     <EuiFlexItem grow={false}>
-                      <EuiButtonEmpty color="ghost" href={cancelUrl}>
+                      <EuiButtonEmpty color="text" href={cancelUrl}>
                         <FormattedMessage
                           id="xpack.fleet.editPackagePolicy.cancelButton"
                           defaultMessage="Cancel"
@@ -451,7 +451,7 @@ export const EditPackagePolicyForm = memo<{
                         <DevtoolsRequestFlyoutButton
                           isDisabled={formState !== 'VALID'}
                           btnProps={{
-                            color: 'ghost',
+                            color: 'text',
                           }}
                           description={i18n.translate(
                             'xpack.fleet.editPackagePolicy.devtoolsRequestDescription',